I've worked every shift, including overnights, and not worked at all. My sleep schedule has been inconsistent since high school. Due to SAD, I sleep more in the winter. This time of year, depending on my obligations for the following day, I sleep anywhere from 4-14 hours. If I have to be up early for work, I usually get 4-6 hours. If I can sleep as late as I like, I'll sleep for 10-14 hours.
I generally just sleep as much as I need to when I can. I'm a night-owl by nature, and with my current work schedule (usually 9am-6pm), I can't get to sleep early enough to get even close to 8 hours on the nights before work days. So I catch up when I can.
Lisa, I've pulled countless 20-30 hour days to get my sleep schedule back on track after a sleep binge. I'd suggest staying up as long as you can to improve the odds of being able to sleep through the night. Do whatever you need to do to get back to your normal schedule.