We rotate them in and go up to our heaviest set that we can hit a triple for a couple of reasons... one that has been pointed out here they are close to impossible to spot although we do it from behind just like a squat, always use the rack and if someone is stuck I always have them squat out of it, shouldn't be but a few inches to get it down to the rack, most guys won't go deep enough on the first one, if you make the set a "make it or miss it" single, they'll probably not go anywhere near depth to make it count, they typically get deeper as the set goes on so we do triples and also cuz they put such a strain on the lower back, it takes a while to build up those muscles if you haven't already and helps a bit with injury avoidance.
Can you say run-on?...