Backpacking is usually a relatively inexpensive hobby. Usually. The basics are pretty cheap. Once you get into high quality down, high tech fabrics like spinnaker and cuben, and custom-designed equipment it might get more expensive, but most of the equipment will last a long time. That's how I justify buying most of this stuff.
Of course, even though my gear tends to last a long time, my tastes change. I hold out as long as I can, but sometimes I just feel the need to replace some equipment before its time has come. It's a never ending battle against my impulses. Let's see how it's going now.
My current favorite backpack is my Mountain Laurel Designs Exodus. It's my go-to pack for almost all of my backpacking trips these days. I got the pack for Christmas in 2008, and it has since seen use on the entire New England Trail, section hikes of the Appalachian Trail, and two-thirds of the Pacific Crest Trail. At least 2500 miles all told. After all that, it is in almost perfect condition. The only damage is a nickel-sized hole in the mesh on one side pocket, and a discolored spot on the pack fabric where I spilled some Aqua Mira. I expect this pack to stick with me for many years to come.
The pack I just bought last year for trips with bulkier equipment, such as the beginning of the Pacific Crest Trail or my (hopefully) upcoming winter trips, is the ULA Circuit. The Circuit is a framed pack that is just as tough as the Exodus, and much larger. Because of the hardware of the frame, it has more points where the pack itself could be damaged, but the one time I had any problems with the pack, ULA repaired the damage and got the pack back to me in no time. I've only had this pack for less than a year, but I expect it will last a lifetime.
I've had a few other packs in the recent past, like my Granite Gear Nimbus Ozone and Vapor Trail, but the Exodus and Circuit are all I need at this point. The Granite Gear packs were still usable-- the Vapor Trail was practically new, in fact-- so I was able to sell them to narrow down what gear I have. I don't think I'll have to get any new backpacks for a long time.
Packs are pretty easy for me. Tents not so much. My ideal pack is as simple as it gets, which is why I love the Exodus. With tents, simplicity is good, but there's a lot more fine tuning that needs to be done. Due to the light weight of single-wall tents, I will probably never go back to the standard pole-and-fly tents, so that narrows things down.
I've had my Mountain Equipment Co-Op Silicone Scout tarp for about five years now, and up until last season it was the only 'tent' I used for all of my hikes. In the Northeast, I don't really need much more. There tends not to be much wind-driven rain in camping areas up here since we have thick forests, and there are often enclosed shelters available when I'm afraid the weather will be too nasty for the tarp. At 12 oz with BackpackingLight AirCore Nano guylines, I can't complain about the weight. It probably could be lighter without the extra grommets and reinforced edges, but it's lasted this long and has kept me dry in plenty of rain storms. For winter use, I may add a few ounces by switching the AirCore guylines for some heavier parachute cord, but that's still not too shabby. I've never even had to seal the seams!
On the Pacific Crest Trail I got a new Six Moon Designs Wild Oasis tarp tent because I was worried about wind-driven rain. The Wild Oasis has 360 degree coverage, which is good. It also has bug netting, which has saved my hide more than once. With the seams sealed and the added guylines, it's about 14 ounces, which is a trivial amount more than the MEC tarp. When I choose between the two for trips now, it's more for functionality that weight. The Wild Oasis isn't very good if I need to cook inside my shelter, and it's more prone to condensation. I'm pretty confident that the silnylon will hold up for years, though. The fabric of the MEC tarp is still perfectly waterproof and free of damage, so I'm quite happy with the money I put into it.
Unfortunately there are too many enticing options for improvement. I've got my eyes on BackpackingLight's Stealth Nano tarp, which is similarly sized to my MEC tarp, but made of cuben fiber (much lighter) and with a catenary ridgeline (tighter pitches). At $320, this one is going to have to wait. There's also the Hennessy Hyperlite Backpacker hammock. At 26 ounces, this would add a lot of weight to my packing system, but hammocks are great for east coast backpacking, where trees are abundant, but flat and open ground is not. I could also go for a single-wall winter shelter, much like the Wild Oasis, but without the bug netting (which would get stuck in the snow).
Sleeping bags are another category where you can have one for almost every occasion, but I think they're a little easier to deal with than tents. With sleeping bags, you can get by with a good 30 degree bag for three seasons, and a -10 or -20 degree bag if you're crazy enough to get out in serious winter. Maybe a shoulder-season (10-15 degree) bag would help, but you can extend a three-season bag into temperatures well below freezing by adding some extra insulating layers.
My most trusted sleeping bag so far has been my 2006 The North Face Beeline. I got it just before the Appalachian Trail in 2007, and it came with me for that entire trail, the entire Pacific Crest Trail, and a few AT section hikes in between. That means this sleeping bag has around 5000 trail miles. I'm not really all that attached to the bag, actually, but down-filled sleeping bags are not cheap, so I've stuck with this bag more out of cheapness than affection for the bag.
The Beeline has seen better days, having been compressed hundreds of times and having probably around two hundred nights of use in total, so I wouldn't try to take it below its 30 degree temperature rating. However, with a little extra insulation (say, a pair of down pants and a down jacket) I feel pretty comfortable in it in pretty chilly weather. That's the great thing about down-- it lasts.
I used a pair of Leki Super Makalu poles for the Appalachian Trail, several section hikes, and most of the New England Trail. Since they have a lifetime warranty, I could have continued to replace the broken shock absorbers indefinitely, but I decided to switch poles instead. It was a good excuse to buy something new and exciting. So I went with the Gossamer Gear Lighttrek poles. Simple, light, and effective. With only two sections per pole, and one moving piece each, these poles are about as simple as an adjustable-length pole can get. And as I've come to discover with most things lightweight, simple equals durable and long-lasting.
I don't think I'll be using the Lighttreks in winter, so I haven't decided what I'll do yet. Either get a dedicated pair of winter poles, or just go without poles. I'm leaning toward the latter, since I prefer having both hands free while hiking in the snow. That limits my tenting options, though, since my tents all use trekking poles as supports.
As I said earlier, simple equipment tends to last the longest in backpacking. My favorite gear over the years has always been the stuff that is the most basic. For instance, after buying about a dozen pairs of specialized trekking shorts, pants, convertible pants, and so on, the best pants/shorts I've found for hiking are the simplest. A pair of Champion soccer shorts. Ten bucks at Reny's, and they've lasted me longer than any piece of clothing I own, they're lighter than any hiking shorts I've found, more breathable, faster drying, and they feel great. For all the expensive shorts at REI, nothing compares to the cheap and easy option.
My other favorites that have come with me so far are the little things. My Victorinox Swiss Army Knife Classic is the only knife I ever need in the backcountry, complete with a nail file and toothpick! Stuff sacks, I still use a few Sea To Summit Cordura bags that I bought four years ago (if you don't let them get eaten by mice, they'll last forever). A camera case made of duct tape and bubble wrap (basically free, and very stylish). Even for writing utensils, the simplest seems to last the longest and work the best-- a 10 cent Bic ballpoint.
I guess the point of this long rant is a celebration of all the equipment that lasts seemingly forever. Sure, you'll probably replace most of it before its lifetime is finished, but it will always be there to help outfit one of your friends, or to go back to when your newer gear needs to be repaired. Even if, like me, you end up with two or three of everything, you've still got the gear to get you through a lifetime of hiking, or at least until something new and nifty comes out. Isn't consumerism great?