Would it be possible to add a way to increase the interactions per day? Like, say, a mission for a hedge witch gives you a boon to sexual stamina. Or discovering  the recipe for a potion that does just that, except the most important ingredient is endemic to a well-hidden and  well guarded grove somewhere.

If not, is there a way to make them character specific? Although it makes sense you can't do twenty people in a row even if you did nothing else during that day (and even then, hunger and dehidration are real problems, as is the need to go to to the bathroom/W.C./loo/whatever-you-call-it eventually), there is no reason why said twenty people screwing each other should have any impact on your stamina or time, right? Why should Bobby and Jess screwing each other while you and your party are exploring a dungeon stop you from having fun with Sarah when you get back?