really depends on your cruise and who's on it..
I have been on cruises where its just me and my friends dancing until 2am.. and other where there are a lot of people dancing until the bitter end.
But to answer your question, how the adult clubs usually work is there is a "themed" event that goes from about 10:30-11:30ish, and then from midnight until everyone is gone, or 1am-1:30ish, they have a DJ playing music with dancing... normal club type music, minus the swear words..