XP: Transition to 2 Naps?

Eitak82

DS was 5 months old yesterday. For a while he has been pretty consistent with a 2 and 1/2 hour wake time, and then going down for a nap (they range from 45 min - 1 1/2 hours). All of the sudden today, I tried to put him down after his usual time frame and he was not having it. He seemed awake, so I brought him out to play, which he happily did for a while more. Then I tried again with no success... finally he went down after 3 hours 15 minutes awake. He was in good enough spirits the whole time, so is he starting to transition to longer wake times and only 2 naps? How old was LO when they made the transition?