We've made the transition from two naps to one. It went on for a week or two: he'd go a couple of days with a totally normal (two-) nap schedule, and then we'd have a rough day where he'd fight the morning nap, or take the morning nap and then fight the afternoon nap and be Mighty Crabcake all day. And then right back to two naps the following day.
A few people advised me to keep pushing the morning nap back by half an hour every day until the afternoon nap turned into bedtime, and I'm sure that's sensible advice, but somehow it just didn't work out that way. On the days when he took a morning nap, he clearly needed it -- he'd be short-tempered and eye-rubby by 9:00, and even if I'd kept him up until 10:00 the previous day, I wasn't about to make either of us suffer for an hour on principle.
And then one day I realized that he would hit a kind of crabby period around 9:00 or 9:30, but if we pushed past it, he got a second wind and played on happily for another couple or few hours. And that was that: one nap at around 11:30 or noon. So far, he's still only sleeping for about an hour and a half, which was a fairly typical length of time for one of his two naps. I'm guessing he'll learn to stretch it eventually. Or not.
He's still sleeping 11 or 12 hours at night pretty reliably, and in fact we moved his bedtime up a bit since the transition to one nap, from 7:00 to 6:45, and he generally sleeps until around 6:30 in the morning. On the weekends, when nobody's up and moving earlier, he often sleeps until 7:00 or even 7:30 (bliss!).
I miss the big chunks of time to myself in the morning and afternoon. I'd got used to eating breakfast when he went down in the morning. I don't like to eat as early as he does (7:00 -- giving him breakfast is the first thing I do when I wake up and Andy goes to work), and he kind of flips out if I eat in front of him and don't share. I've started giving him a snack before he naps, around 10:30, and I generally hold out and eat with him then. And luckily he's really great about entertaining himself and not getting into trouble, so that even if I don't have as much solo time, I have plenty of opportunities to, say, read a book or write a blog post without his needing me every five minutes.
I was at a shower this weekend, talking to other mothers of babies and toddlers, and few of Ben's age-mates in the group had bedtimes as early as his. I have to say, that kind of strikes fear into my heart. From the first weeks of sleep-training, the hours between Ben's bedtime and ours have been a gift. To watch TV, knit, do fiddly little projects with sharp tools on the coffee table. To relate to one another as adults. To give the poor dog a break. I know eventually Ben's bedtime will get later. And it'll be fine, we'll deal, it'll be the new normal, and I won't miss those hours as much as I think I will.
But please, not yet! Not soon!