If I believed in rationality, I would get confused at some vacation policies in the US. You pound a guy for 70 hours a week for 6 months straight. Give him 2 days off, while he is supposed to be attached to his cell phone, lap top, and a fax machine. I don't think in the end it will increase productivity.
Kind of like the Laffer Curve, there has to be a productivity curve. If you work zero hours a year, your productivity is zero. If you "work" 365 days a year for 24 hours, your productivity is zero because you will be in an insane asylum. The magic is finding the right number. How hard can you work, until your productivity declines?
We need to take play as seriously as work. The problem as I see it, and as others have mentioned is that many people don't really get a true vacation. A true vacation means no umbillical cord to the office. You are a free agent, free to take a holiday from work. I would suspect that the days a worker needs for vacation to be productive, would actually drop if middle management types actually allowed people to not do paperwork and return phone calls, while they are enjoying their holiday time.
Product possibility curves show decreasing worker productivity over time. Vacations are necessary to keep workers going.
I am studying to be a history teacher. One thing I will enjoy is the long summer break, which makes up for the low salary. However, I do not think I could just sit around for 3 months; I would need to still do something, perhaps help teach summer school. I probably would head to Florida for a couple weeks though. That said, I am considering changing my major to journalism, and journalism is exceedingly stressful with tight deadlines and not much vacation (unless you are a tv anchor). Oh well.
One thing is for sure: workers should get a decent amount of vacation....anything less than a week really does not refresh you for very long after long stints with no breaks. I no that is why a 4 days or so of a long weekend college break really do not help me. I need a full 7 days to be refreshed and ready to work my butt off at classes again. But, the European breaks are just ridiculous for most jobs. Teachers in America just get the extraordinary "break" (and really they have to come in over the summer and also plan lessons for the fall so it is not a true complete break) beause the kids get that break as well.