I think I probably sleep poorly (based on my criteria above) about once every other week or so. I definitely wake up sometimes before it's time to wake up and lie there for awhile, but I can't remember a time when it's taken longer than 30 minutes for me to get back to sleep in any of those cases.

If it's less than an hour before I'd normally get up, and I'm awake and feel like I want to get out of bed, I just get up early that day and am a little more tired when I go to bed that night.