[kevin_nisbet]

While this only works with instances, I usually just cron the shutdown command with a future time. Nice thing is, if working late I give myself a couple hour window to cancel shutdown on any nodes I'm still using.

echo "0 22,0,2,4,6,8,10 * * * /sbin/shutdown +115" > /etc/cron.d/autoshutdown

I'm all for a better tool, just wanted to point out a builtin alternative.