As far as I know, and Harem Hotel was pretty much my first NSFW game so I know quite a bit about it, there's no time limit. You can literally do whatever the fuck you want to do as the days go by, the things is that as you go through the game the events require higher stats with more and more girls. You can level them one at a time or multiple at a time, it's up to you.
And also there's the catch of certain things, events and other stuff being locked behind multiple girls and stats, like the dungeon itself. So yeah, just play the game, spend time with the girls you want and don't worry about time limits.