Putting him in later may actually make it harder for him to go to sleep - if he's OT. He's roughly the same age as my dd, and 6 hr of A time would really be maxing her out. So I would aim for between 5.5 and 6 (depending on whether he tends to be high or low in terms of sleep needs). If he didn't go to sleep at all today, then it might be time to step up your level of intervening - it looks like he thinks it's ok to do whatever in his room instead of napping. So I'd do a modified wi/wo - every time you hear him get out of bed, go in, take him back to bed, tuck him in, say "it's time for night night" (or whatever you use for naptime) and walk out. Don't talk to him other than your "catch phrase" so to speak. It will probably mean for several nap times that you spend the entire nap time doing wi/wo. The more consistent you can be, the sooner he'll understand that nap time means he stays in bed.
