Are LEGO minifigs' arms supposed to come off? I can get the arms off my LEGO minifigs, however, will doing so repeatedly wear them out?
No, they are not meant to come off (and neither are their hands) and I imagine that doing so repeatedly will cause them to become loose, as is the case with hands.

I have noticed that the hands come off a lot easier nowadays compared to 1970s/1980s vintage Lego, but I'm rarely sadistic enough to rip their arms off :)