I would tend to measure in terms of "shave weeks/blade". The main variables are the thickness/amount of hair to be cut, and the regrowth rate.
Personally, Mach 3 gives me 1 shave week/blade… Whether I shave daily, twice a week, or even just once, the amount and thickness of hair compensate to basically make any additional attempted use of the same cartridge a game of "how much would you like to bleed?"
Just to give you some baseline info, I usually feel a little hair coming back 8-10 hours after a shave, and downright fuzzy the next day. I usually go 2-3 days between, though, otherwise I have a hard time getting a GOOD shave that can grab/pull the hair the right way as it slices.