Depends how often they fight someone like Floyd who fights once a year will have more free time than someone who fights 3-4 times a year. Up and coming fighters I think should probably be training most to be ready to fight anytime of the year but also to work on things that could help them reach world level.
Unlike Pac who's on drinking binges.. Or gambling that's even worse. This is why he has no money from his fights. Advance after advance from Arum = $0000000.0000
During a training camp, very little free time. Outside a training camp, really as much as they want. Some like to stay in and around the gym to keep in shape, others like to let themselves go a bit (Hatton, Duran etc).