I usually just try to finish them off. Lots of high stakes players sit out and say "please rebuy" over and over. Kinda sounds condescending to me and seems sorta like a dick move.

it depends on the opponent. if i think they're likely to donk off their last few chips, i keep playing. if they seem like they will play hard, then i'll often stop.

when i do play, i usually starve them wait for a relatively big hand before i go crazy -- there's no reason to give them lots of action if they can't give it back.