The game is pretty nice, but I agree that it should not be stretched much. Most of the fun is in the corruption of the characters and how they deviate towards more and more perverted versions of themselves, so once a certain point is reached and you can fuck anyone mostly freely, there wouldn't be much more to do. Plus, if I remember properly from when I played, all happens 2 weeks before that nuclear solution that is talked about in the intro, right? So there isn't much to do, really.
Seeing a new game in the same spirit (many girls, gradual corruption, exhibitionism, NTR, that kind of stuff) would actually seem the better option in my opinion. Once this is properly finished, of course.