Unfortunately, I cannot add any constructive comments as both my two children are excellent sleepers.
My eldest (now nearly 9) has always loved her sleep. As a young toddler, she would fall asleep in the afternoon at say 2 pm, wake about 4 pm and still be in bed by 7:30 pm. Because I was working part-time, three days a week she had to be up by 7:30 but, because my mum was looking after her, I never had to feed her her breakfast or get her dressed. I would literlly wake her up and be out the front door. My mum would then give her breakfast, get her dressed, etc.
My youngest child (now aged 4 1/2) absolutely loves going to bed. On a Monday, I look after my niece and nephew after school and they are not picked up until gone 8 pm. My nephew is 2 years older than my son and they absolutely adore playing together, but when it comes to about 7:15 my son will actually ask to go to bed, even if him and his cousin are in the middle of a game. He is always in bed by 7:30 and normally wakes about 7:30/8:00 in the morning.
I am not saying I have perfect children (far from it, believe me) but I have always been quite strict about bedtime from a fairly young age. I love my sleep and just could not bear the thought of having disturbed nights or trying to get an unsettled child into bed (although that will change for me slightly as I am due to give birth in about 3 weeks time).
The only problem I am now finding is with my (nearly) 9 year old. She has no problem in going to bed at, say, 8:30 but it is the "going to sleep" that seems to be a problem.
Because I am currently 37 weeks pregnant, I am into fairly early nights (about 9:30 is the latest for me) and, invariably, when I go to bed, I find she is still awake. She is not playing or anything, just lying in bed trying to get to sleep.
Me and DH are going through rather a bad patch at the moment (I post under "should I stay or should I go") but I am quite sure that my DD is not really aware of what is going on. I saw a good friend of mine last night for a coffee, and I told her some of what we are going through and she said that she would never have guessed in a million years as my DH puts on such a good front in front of people. He doesn't shout or argue or anything like that when we are alone that my DH would be aware of, he just gives me the silent treatment and has "nasty" conversations with me.
I have been asking my DD if anything is bothering her or if anything is on her mind that is stopping her going to sleep - we do have a good, open relationship, but all she says is that she can't switch off and go to sleep. I have tried to stop her doing anything stimulating before bed time, normally she will do her "reading homework" to me before she goes to bed as a "quiet down" time but she just seems to have a problem of actually getting to sleep.