I've been following a book I got from the sleep store - sleep easy solution and it says that for babies of around 8 - 9 months old they should be only having 2 naps a day.  The first time they wake up in the morning, it suggests keeping them up for about 2.5 hours and then three hours between nap one and nap 2 and then they stay up until bedtime.  I keep to this routine fairly strictly on the days I am at home but if out and about I'm a bit more flexible.  Also this routine works best if bubs has two decent naps, ie if he only has two short ones and its only 2 pm and hes already had 2 naps then its a long stretch to bedtime but there isn't really time to give him another nap. 

That was the other thing the book said, make sure they are up for at least 2 hours between end of nap 2 and bedtime or else they will not want to go to bed.  I get around this by varying his bedtime each day, so he may go to bed at 7.30 one day and 8.30 the next depending on how long he napped for that day.

Apparently sometime between 9 and 12 months bubs will start to show signs of wanting to stay up even longer (my wee boy is already showing these signs and he only turned 9 months today).  When this happens, the book says to increase the first time up to 3 hours and the next time up to 3.5 hours.  It says not to drop to one nap until after they turn one.