This is great! One simple way to add variety and difficulty is to say that every edge in a day has to be different. A different combination of technique, location and how you’re dressed (major categories, clothed, PJs, naked or slutty as a max on that).
Beyond that have a really good punishment for accidentally going over. 30 band snaps to your clit, or rubbing with menthol or plugged all day, whatever works for you really.
If you love being wet, add a rule about not being allowed to change panties during the day, so you’ll get messier and messier towards the end.
If you have a suitable toy then pick one night a week you have to sleep with it in you, and every fifth day you’re not allowed panties, for example.
Let me know how you get on and we can tweak as we go!