I built all my bikes from frame sets, so when I put them together they've been overhauled. I've never torn one of my daily riders completely down..... seems like a waste of time. I have changed stuff out here and there as needed - BB's, headsets, wheels, etc.

I'm a bit of a maintenance freak though..... I'm always inspecting and my bikes are always clean, properly adjusted, and lubricated. If I pull one down to go for a ride and something is amiss, I set it aside and choose another. I have a 4 bike rotation.

Any used bike I get I completely tear down and build back up before re-selling. That's the only way I can be sure it is going to be trouble-free for the next owner.