Geez, do these guys ever rest and take vacations like the rest of mortals?
The problem is that there is no proper build up to the Australian Open (in terms of Masters events). So I think players feel the need to have trained hard and got some match practice in prior to that - hence all these exhibitions and training camps.
Instead, Federer has opted to build in holidays within his regular ATP calendar. In fact, he took a much longer time off after Wimbledon than during the official off-season. Rafa skipping Paris might be a sign that he may soon look to do the same.