Parents often ask me how much sleep their child needs at night. There is just no magic number; it varies from child to child. The average for all kids, as early as the third to fourth month of age, is eight to ten straight uninterrupted hours, but this depends on how much they nap during the day. The ideal bedtime is when both parents have had an opportunity to giggle and read with the kids, then say good night and still have time for themselves and each other. For this reason, if one or both parents return home late from work it may be worth it to delay the child’s bedtime (within reason). That said, I find that school-age kids rarely wake up happy if they’ve gone to bed past ten the previous night.
The worst reason to let a child stay up late is because he doesn’t want to go to bed. Jimmy may fight sleep just to stay up and be part of the action, but you must be firm.