Depends on the scope and mount. Accucam type mounts should be right on.
Mine is. With an Aimpoint Comp2 I use a GG&G QD Accucam cantilever on my AR.
I take it off and put it on every time I shoot and haven't needed to re-zero since day one. And that's been many times over the last few years.
Plus I have it co-witnessed with my irons so if it's off I'll know right away
Not sure about the stock Aimpoint mounts, I hear they are good if you are up close but can be off a little at longer ranges when you put it back on, YMMV