i never leave because of gear unless the gear is exceptionally bad, like 20+ ilvls below the dungeon for example. in that case i feel leaving is justified. nobody should be forced to endure grouping with players that are lazy about their gear. poorly geared tanks make the healers job more difficult, poorly geared healers make everyones job more difficult, and poorly geared dps might as well not even be there because they arent contributing to the success of the run. ive seen dps in AK wearing lvl 38 gear and tanks in SV wearing lvl 15 stuff. im sorry but im just not going to put myself thru that

on the subject of time however, there have been occasions where ive had to leave the dungeon early or at the start if i knew i wouldnt be able to finish it. i have a job where i am on call and could get called in at any time. an option for shorter roulettes with obviously less rewards would be a nice option