I just saw this post and just wanted to jump in and reassure you that dd is doing the same thing here. Hit or miss on the nap and VERY fragile without it...melting much earlier in the evening so she definitely needs one. And she takes atleast 2 hours when she does take one so it's definitely needed. I personally don't know that it's about wind down so much as they're just taking control a bit more, a bit more independence. I often think that she's staying up just cause she can, YKWIM. She's figured out that I can make her stay in her room, but I can't make her sleep. We do leave her in there for as long as we can for a rest period. A couple of times, we've been able to go in and tell her to get back in her bed (if needed) and that it's time to sleep and she will, but not always. I really think it's just a sign of asserting their independence and I figure atleast she's getting some alone time. It is VERY frustrating for me with a new baby, especially if I happen to get the baby down at the same time and then dd doesn't sleep so I can't really sleep, though I doze as much as I can through her chatter down the hallway. So, no magic answers for you, but definitely sympathy. And the time doesn't really matter here either...I've tried early and late and being consistent with one or the other. We actually let her sleep pretty late and she still goes down for the night miraculously enough. Hang in there!