Well, there you have it! I guess there isn't a maximum, or one hasn't been reached yet. But, wow that's a really slow exp gain, 4.5 days per level... Gives me A LOT to look forward to... *sigh*
Well, you don't necessarily have to encounter a maximum to write about it. You just did, lol. You said right now it is higher than 80 per position, so even that would be helpful to put on the wiki page. =P
I simply made the initial assumption about maximum stamina based on aesthetics, and even admitted it was pretty stupid. But shortly after, I also assumed there was no maximum. But simply the devs didn't design the game UI to handle stamina above a certain number of digits without looking "messy" and overwriting other areas of the UI screen, probably because it is so hard to reach those levels. The maximum stamina obtained in game right now seems to be less than 8k (after skimming the top 50 rankings), so probably no one has even come close to hitting 999 with a single girl yet. Has the game even been out for long enough yet for that? Anyway, I actually found 7.3k, but my stamina is no where close to that yet, either. It's only at 5.2k, and my leveling speed is slowing way down already. My max girl is only 580. My short term goal was just to hit at least 500 with all tier 2, 3, and 4 girls, then I'll go back and level tier 1 as much as I can.
Oh, btw, what happens if you reset while there are girls being filmed or in a practice session? I remember seeing something about that a while back, but can't remember. I even tried to find it, but couldn't locate the related post.