balloon, i got that 2 hour break too until dd1 was 3 1/2 despite being my parenting being all over the place ( "she who cannot be named" would probably have me burnt at the stake ).
i truly believe it is nothing to do with the way you parent and everything to do with your children's needs and temperatment. both my dds never slept as babies unless held or in a pram, and even then only for 30 minutes at a time. both of them started to get into more of a napping groove at around 6-7 months and were napping beautifully by 12 months. nighttime sleep a completely different matter though!!
sorry- not meant to be awkward to you (isn't that simultaneous nap just bliss), but I still have vivid memories of being told by a particularly smug gf follower at a playgroup that dd1 didn't sleep through because "it's your fault. have you not heard of gf?"
hence the name is forever associated with that very unpleasand mother...
but, to stop ranting, I am pretty sure that whether your child stops napping at 13 months or 5 years old is pretty much down to the child, rather than to anything you do...