The 'standard' advice, from people like 'Supernanny' and other recognised childcare 'experts'(?) seems to be that:
(i) young children should have a consistent bedtime (i.e. they should go to bed at the same time at weekends, and during school holidays, as they do on schooldays, even if that means their parents having to leave a social gathering earlier than they'd wish to) ; and
(ii) that young children should get sufficient sleep to ensure that they're bouncing out of bed in the morning (rather than be dragged out of it).
What the 'experts'(?) seem less able to agree upon is the exact number of hours sleep that young children need. (As an analogy, it used to be assumed that adults need at least 8 hours sleep per night but recent research suggests that 5 or 6 hours sleep is actually better). Most 'experts'(?) would probably suggest a bedtime of somewhere between 6.30pm and 7.30pm for a 5-year-old but if he's leaping out of bed, full of energy, in the morning then there's probably little to worry about.
When I was teaching (at secondary level) I was often concerned to see that I was working with young people who clearly had insufficient sleep. (My lessons might not have always been the most interesting but when a youngster fall asleep within a minute of sitting down at his desk there's obviously something wrong!). So you might think that I'd be automatically supporting early bedtimes but (because everyone's different) I think that the 'bouncing out of bed' test is probably far better than any specific bedtime.
Chris