DD has just turned 4 and probably 4-5 nights out of 7 she will be in bed by 7.15 and sleep until roughly 6.30am without waking. But then for the other nights she will be in bed by 7.15pm, but doesn't go to sleep until 9pm or after. I then have to wake her up as we have to leave the by house by 7.55 to get to nursery at 8am. She isn't having a sleep at nursery (or at least not to my knowledge).
DS had periods of doing this but it was always because he had had a nap in the afternoon thanks to gp, lol!
What sleep patterns do your 4 yo have?