Depends. Follow your doctor's specific instructions. A few generals tips would be to walk and exercise enough each day so that you are tired at night. If you need to nap during the day, limit the naps to 15-20 minutes and do not nap after mid afternoon. If you sleep too much during the day, you will not sleep at night. If pain interferes with sleep, use your medicine to get comfortable before you go to bed.
It varies. There can be a number of reasons one might not sleep well after spine surgery. It may be the pain, the lack of activity, side effects from the medications, boredom, depression. Although it is a generalization, i think my patietns do better the quicker they can get into as normal a routine as possible (within their activity restrictions). Thank you for the question.