[newaccount74]

If you ride your bike a lot, and some point the bearing races in the hubs will wear out and you'll need new hubs, same for the bottom bracket, the rims will either get ground down by the brakes or get a dent that requires them to be replaced, fenders will get bent and / or rust off, screws corrode, brake / shifter cables need to be replaced every few years...

Bikes that get ridden a lot are like the ship of Theseus...

[snotrockets]

Maybe that's the problem, I only ride 15,000km a year or so (used to ride more when I was racing, but life came in the way)

[newaccount74]

That is a lot more than I ride :)

You must have cared well for your bike if it lasts 40 years with that kind of milage.

[snotrockets]

Mileage is split across multiple bikes.

That specific one is 40 years old, but I only owned it for the last four. All my bikes were bought used: like cars, once you roll them out the shop's door, you loose a significant amount of the purchase price.