did-you-kno:

The perfect length of time to be on
vacation is 8 days. Your health and
wellness levels rise rapidly while on
vacation, but they peak on the 8th day
and return to baseline within your first
week back no matter how long you’re
gone. Because lengthier vacations
don’t seem to make a difference,
experts say the key to improved
overall satisfaction is to take more
vacations, not longer ones.
Source Source 2