The wheels I've built myself usually need a little re-truing after the first few weeks of riding. There are usually a few places that are 1-2 mm out of true. I guess I am not doing a good enough job with spoke windup or something. After that touchup, I check them about yearly and they don't need anything. I'm sure if I abused them, they would (need re-truing), but I don't (abuse them). I ride on the street, don't jump curbs, and stand up or hop at major road irregularities. I think it might depend on how OCD you are. If I had a micrometer and was obsessing over 0.1 mms, I'm sure I'd be re-truing all the time. An out of true has to approach 1 mm before I think it is worth unmounting the wheel and setting up the truing stand. I used to be more fussy but then I got a life :-)
This. And I don't bother with the stand after the initial build; just put the bike in the stand and true with the brake pads.