I'm pretty sure when I was on Oasis in January that they sold the drink and internet packages right up until Thursday of the Saturday to Saturday cruise. Might have been Wednesday for the drink packages, not sure, but it did go pretty far into the week for those who just wanted the packages for the last 2 or 3 nights after our days in ports were finished. There are several drink packages depending on what you want to drink as well.

Whether you prepay the gratuities or not is a matter of whether you just want it out of the way or not. Not sure if their rule that those in anytime dining have to prepay is still in effect, as we had first seating.