Are you using latex or silicone caulk?
It's my opinion that the latex needs longer to cure before repeated moisture exposure. I would recommend a minimum of 24 hrs. for silicone, and 48 hrs. for latex.
I would also seal the shower 24 hrs. after caulking (if using latex), and let dry overnight. If using silicone caulk, you can seal 1st, then caulk the next day.
Either way, you're 48 - 72 hrs. before using your shower.