Day 1: Left laptop in bag all day.
Day 2: Read some email, built a snow fort.
Day 3: Casual hacking, poked at old code for a bit (with eggnog).
Day 4: Wikipedia party. Compiled a bit of code. A little bit of Facebook.
Day 5: Stayed up late building a RSS generator for yet another language; parsed XML without XPath.
Clearly, the optimal length of vacation in 4 days.