Back in college, I once worked as a mechanic at a bike shop. Most of the parts were obtained while I was at the shop; some free, some bought off customers used, some parts from a bin at the shop, some I bought once I had a bit more cash. It started out as mildly used frame with a front derailleur hanging off of it. It was a 95 frame and most of the parts are from the same time period.
Today, it is still my one and only mountain bike. While I'm no longer an avid rider, I still go on bike rides with my kids every couple weeks or so. Feels like an pair of well broken in leather boots.. familiar... comfortable. IIRC, the only parts replaced post 90s are the twisty shifters (Sachs ones failed over time) and the bumpers in the Halson fork (I gained weight... lol). No longer use the Shimano clipless pedals but I still have them. Its a Frankenstein of parts but holding up to the test of time.
For a short period of time, I joined a group of road bicyclists. I ended up with a 97 R200 Cannondale. I had a bit more money at that time... purchased new.. all with original parts. I still have it but it doesn't get ridden near as much as my mountain bike.
Just wondering if anyone still primarily enjoys an old bike and have no real reason to get rid of it...