Ok, I confess, I've posted this same issue here:
[ubuntu] Laptop Hibernation Delay - Ubuntu Forums

But with no replies yet, I'm grasping at straws to get an answer, and I don't think this is a Ubuntu specific issue.

Here's the gist of it:
I want to get my laptop (dell mini 9, running ubuntu 8.10) to suspend when idle, then after a further delay, say 1 hour, wake it self up and hibernate.

Windows XP seems to be able to do it, Ubuntu (to the best of my knowledge gleaned from google) does not.

Could anyone explain how to make a laptop suspend on a timer, so it can wake up later to hibernate? Because that seems to be the primary issue.