I just try to pace myself, more than go by a set number of shots.
I take a shot, look around, step back, stretch, see what the other guys around are doing, bs a little, take another shot, repeat. Every couple of shots grab the barrel and if it feels really warm to the touch, I wait a couple more minutes. I always leave the bolt open between shots to let alittle air flow through. Don't know if the heat affects it much, but I think of it this way, "how fast can I afford to throw three dollars down range each shot?". That's kind of what you're doing each time you pull the trigger when you're shooting the larger calibers.