I'm not using anything from my Scouting days in the 1970's. But I still have my BSA pocketknife. I prefer a SAK, but maybe I should bring it on a trip. I got it late in Cub Scouts in 1973, so that's coming up on 40 years.
But in the mid 1980's, I worked in a backpacking store and developed some of my own UL techniques (no tent, no stove, no sleeping bag). The gear and the techniques weren't as well developed as they are now, but:
I just used my Alpenlite UL "day and a half" pack last week in Hawaii because with the wife and kids along, I needed more lightweight gear. It's not much heavier than today's offerings, given that it has a foam back pad/stiffener. I got it in 1984, I think, so 29 years ago.
I've still got my orange and brown Thermarests from that era including one with a brass, not plastic valve, and still use the brown ones with larger groups - so those are 26 to 29 years old.
I should have brought my MSR whisperlite (26 years old?) or my Optimus 8R (30 years old) because I couldn't find canister gas anywhere on Kauai and ended up cooking Top Ramen over Sterno (whereas, I did find white gas at Walmart). Actually a stove head for standard propane cylinders or an adaptor would have even easier for sourcing fuel.
A little of my polypro from the 1980s is still in the mix. Patagonia Baggie Shorts last forever, or at least more than a quarter century.
My oldest sleeping bag is a semi-rectangular synthetic by Caribou (1985). The weight-saving aspect is that I have a slip-cover for the bottom that holds two thermarests and the bag itself unzips flat and serves as a double-wide top (early quilt concept). Hence, my wife and I can share the weight of one bag. There are other benefits to that arrangement, as well.
My oldest tent is a Jansport "Yellowstone", 3-person, 3-pole free-standing dome (1984). Not at all UL, but it goes on canoe- and car-camping trips still.