Latest you can purchase drink package on 5 night

[dmcgeary]

What's the latest time you can purchase a drink package for the remainder of the cruise on a 5 night cruise?  For example, can I purchase the package on board on the 3rd day for the remaining 3 days of the trip?

 

Thanks for any info

[Clarea]

Royal's rules say there must be at least 4 days left in the cruise, but I've been on ships that allow purchases later than that.