My lo went ot 1 nap at 9 months - he'd started NWs and EWs, so we cut out his morning nap. and hey presto, problems solved. Very occasionally he will have two naps - if he's had a bad night teething, he'll have a power nap mid morning say 30mins, then a short afternoon nap. My lo is spirited, and doesn't need much sleep, survives well on a 1.5 hour nap (sometimes less), and then 10.5 hours a night.