It really depends on how much you plan on dri nking and what type of drinks. Alchohol vs non-alchohol. Most ships will sell both types of packages.

For the alcohol they will probably sell two versions. This will very much depend on what drink you can get "for free" on the package. It can be really difficult to get an actual drinks menu with prices of all the drinks. We decided that we didn't drink enough to buy a package last time. I like soft drinks so took a 12 pack of cans on board to keep in the cabin and just bought a couple while out and couldn't be bothered to get one from the cabin.

Most likley you can buy a drinks package at anytime during the cruise. this will be prorated to the number of days left.

I found the tips/wifi/drinks prepaid to be bad value on Celebrity. Mainly because the wifi was only good for checking email and I needed to pay to upgrade to something useful, didn't drink enough to pay for the drinks package. They actually tried to pass off a margarita made with beer on the basic drinks package. It was horrible and you could always pay the difference in price between the free drink and the "premium" drinks. Just too complictaed to be bothered since you never really knew what was "free" and what had an extra charge. I always prepay tips because we don't eat in the main restaraunt where you are expected to leave ectra tips for the waiters anyway.