I wondered about the length of time between sleeps too.  When my two were this little I kept them up for somewhere between about an hour and an hour and a half and then put them back to bed regardless.  Having said that, using the Plunket tired signs is a fantastic way to decide when they need to go back to bed.  Even now at almost 9 months at the first sign I will put DD straight into bed.  I find that if I wait too long after seeing one of her signs it can be too late.

And I'm also with those who say it's not a bad thing for them to lie in bed awake if they are happy.  I leave both mine in bed until they tell me they want to get up.  If they are awake and happy then I figure they are having a rest / getting some time out to themselves / learning that bed can be a positive place (so I avoid those bedtime tantrums later on down the track).  Both have been known to wake for about half an hour and then just go back to sleep, even after chatting away to themselves.

Hi Hopes, congrats on the birth of your little boy .

When my boy was your Sons age I basically kept him up for approximately 1 hour (or less if he was showing his tired signs) and during that time I'd feed him, change his nappy, have floor time/cuddles then usually he'd be back in bed again for a few hours.  We did folowed this 'routine' for ageeeees.  I think from memory Plunket suggested this routine so we just followed it and it worked fine for my boy.

How long is your boy up for?  Perhaps he's getting overtired from being up too long or is overstimulated?  I found it pretty hard to read my Sons tired signs for ages which is why the 1hr up routine we followed worked so well.  If he wasn't tired for some reason I'd just get him back up for a wee while.

HTH

xx