My DS will be one tomorrow. He's never taken more than one nap a day (except when teeny tiny). For the last few months he's been fighting his nap more times than not. The last month has been nearly impossible. We'll leave him in crib an hour in hopes he'll give in, but no. He just cries the whole time.
I don't know if it's his age or the fact that so much has changed. In the last two months we've moved, brought home baby #2 (she's 5weeks now), and he's getting two new teeth.