Considering you get to go spend time with your primary, and probably neither you or them would agree that you couldn't be sexual with them for X amount of time? If that isn't the case, that would not be very fair to ask of your girlfriend.
And I do think choosing to let her know you would like X amount of time between her being intimate with somebody and your next date in general can make sense, but probably not the best long term solution - what if you start dating somebody else someday, and then you can't be intimate with her because you can't schedule your dates X amount of time apart, or she starts seeing somebody else, etc.
I imagine this is just a temporary thing, so hopefully you are working on working through it instead of wishing you could put rules in place so you don't have to feel crappy.
Sorry if anything I am saying is off base or I misunderstand your situation with your primary, working on too little sleep here.
Happiness will never come to those who fail to appreciate what they already have.