Once you get it setup the way you like as far as action goes, I wouldn't do a "setup" unless there was a compelling reason to do so. Compelling reasons would be the intonation starts going off or if the action changes noticably. Differences in humidity and temperature can require tweaks to the truss rod. If you change string guages, you may have to tweak your setup to adjust for the different string tension.

I've experimented with the setup on my strat quite a bit before I got it where I wanted. There's always a trade off between low action and fret buzz. I also messed around with pickup heights. Now that it's where I want it, I leave it alone. Otherwise I be endlessly tweaking my setup rather than playing! :-).

My LP I've left with the factory setup. I'm happy with it.