I've got a regular night here (copenhagen) where I'm the only DJ because its not enough money to bring any guests thats a 5-hour shift which can be pretty brutal. luckily the bathroom is right next to the DJ booth, so its a quick run between records if its not a busy night. the environment is less of a club and more of a cosy restaurant bar, so there isn't as big of a demand to play uptempo the whole time. thusly, I get to play some nice deep numbers and b-sides, which I'll usually start with for the early crowd then work my way up to uptempo.
on our other night though at a proper raging club, we have 2 resident dj's and usually one guest. if its not a guest night, we'll split the first hour in half (my mate plays rare garage) and it gives us both a chance to show our styles a bit, then switch off hourly. it works out great. guest nights, we usually try to do 45 minutes for each so that everyone gets time to play, dance and mingle.
I know the feeling like you're being dragged off when you're really in the zone with a set, but that means you can just come back with more firepower on your next set. best to leave 'em wanting more has always been a motto for me.