I tend to take all mine off at once, so that I can clean the fretboard. Changing them every 2-3 months means that in that time the fretboard has built up quite a light level of "gunk" that comes off easily.

I don't find that the strings take long to settle at all. I put them all back on with lowish tension, bring them up to tune, approx, give them a little pull then retune properly to pitch. They sometimes need another retune about an hour after that, but it's never been a problem for me.

The pins on my Martin never need pusjing down hard, but on the cheap Falcon I use on camping trips, if I don't give them a real push, they're likely to pop out when I apply tension.

I have a mate playing in a Pink Floyd tribute band who changes them before every gig on all the guitars he's planning to use (4 or 5 usually). Personally, I think that's a bit excessive, but he says he can hear the difference.