This happened yesterday and I have been mulling it over, but I a sure IANBU.
DS2's DLA forms are due for renewal, he is 4.9.
He sleeps very badly. He doesnt go to bed until about 9pm, then he is awake again by 1.30, back down by three and then awake again by 5. Sometimes he will go back down but mostly thats it and we are up for the day. When he is awake I am awake - normally in bed with him signing or reading stories. Melatonin hasnt worked, a sleep specialist from the LA couldnt offer any help except putting a lock on his door so he cant get out 
I took the forms I had done to a welfare rights drop in. The benefits advisor told me that this isnt much different to the sleeping pattern of most children under 5.
I am sure she is wrong. DS1 slept much better than that and DD who is 3 sleeps all night.
Do/Did your 4 year olds sleep like this?