Because he felt his days were numbered.
Duty. Honor.
HINDsight
Wait I freed?!?!?
2nd Monster: He's at medical school. 1st Monster: Oh what's he studying 2nd Monster: Nothing they're studying him!
Udderly useless.
PEEr pressure!
Because it's his only chance to open the door to Number 10!
Because it's two gross! (A gross is a measurement unit for "144". So 2 * 144 = 288. Or "two gross".)
It's days were numbered.
He wanted to take a month off.