The problem with having nice long vacations is that you fall too completely into the vacation rhythm. You have time to fully adjust your schedule.
During a short break you're constantly catching up: getting your teeth cleaned because you can finally spare the time, vacuuming the carpets that only get vacuumed during breaks, tying up loose ends from the frantic last two weeks before the vacation, and then turning right around and getting ready to go back.
On the other hand, on a long break you have time between the catching up and the getting ready to actually fall into a routine: having a leisurely breakfast, going to the gym, reading in the evenings, cooking nice dinners. By the time you have to start getting ready to go back, you have a whole new schedule that gets interrupted.
I think the solution is obvious: make all breaks longer and more frequent, so that the work-time schedule is the anomaly, coming in brief spates, and the relaxed schedule is the norm. It also would reduce or eliminate the catching up period at the beginning of each break if breaks were frequent enough, so they wouldn't need to all be 3-4 weeks long for full effect. I think perhaps a week off each month would do the trick.
Feel free to suggest this to your employers and educational institutions...