We are approaching #30 with Royal (61 overall with 8 lines) and never witnessed anything like that. Yes, some people could overindulge (maybe saw a couple of them)... but it is not something usual. Even on Carnival we have not witnessed this.
Let put it this way, nothing different from several cruises from UK,
Hmmm from what I know many people in Europe think that people from Britain often have party attitude. I do not think it is related to the length of vacation...