In this case it's simply about ending one great story and starts another, same or similar theme (incest and cheating - because son fucking his married mom is both, the same for father/daughter), so i would avoid harem and stuff, because that would be just "simple sex" no taboo. So i would always simply close one story after max 5 chapters, and start another , fresh one. I said that million times, and still artists insists with extremely long stories, because evidently people are asking for that, and i can't understand why on earth would someone find exciting same characters fucking for 150th time, instead of seeing new ones , especially in incest theme, where build up, and first sex are fundamental and most exciting.