
I have the same thing with my 2 staffords, when is it enough?!
I usually let them play until the teeth are flashing and if they are getting more excited (zoomies :) ) I will stop it and tell them to leave each other alone, if they keep going on after theyve been told they are crated to calm down for 10 mins and then let out and they hardly never start again (at least for 15 mins lol) they usually just go and chew a bone or have a cuddle, di you have a crate? If not buy one, it will be the best purchase you ever made and its ideal for dog to have time out in as its their den in their eyes and they dont mind being in there rather then being shut in a room alone and no way of seeing through you know?
You have to stop them when
you feel its needed unless the time calls beforehand, its not when the dogs decide to finish it but you as you are in charge and control, it also proves your 'top dog' to seperate them same as a alpha wolf would etc and just shows them you are in control not them.
If you go on when
you feel comftable then they will usually learn the limit their allowed and stop there, our girl is 2 1/2 and our boy is 6 months so they do get pretty rough still but Im always there to stop it and thats the most important thing, a few scratches here and there wont hurt but if you find proper bite marks (IE teeth marks top and bottom and any open wounds) closer supervision is needed but with bullbreeds everything looks and sounds so much worse then labs for example fighting together and it can sound scary, its all brazon and loud with bullbreeds and that doesnt help judge the level of excitedness does it!?
Maybe try distracting them with a toy when they get too rough for your liking and then get them playing a game of tug together, works a treat for my 2 :)