Once upon a time, when the clock struck the magic hour in a land where the bedroom's centrepiece was the bed, children would quietly listen to a story until they slept peacefully through the night and awoke feeling alert.
Today, the electronic paraphernalia of many a bedroom has turned it into a time-free extension of cyberspace.
Are we too lax with their sleep ? When should they go to bed and how much sleep do they need?
At all ages, there are natural differences in sleep needs. Healthy five-year-olds need 10 to 12 hours, eight-year-olds need nine to 11 hours, and for early teens, eight to 10 hours is about right. But don't forget: the earlier to bed, the sooner they'll wake up.
Daytime naps are not usually needed beyond age four, especially as it delays bedtime and shortens night-time sleep. The key to adequate sleep is whether children get up fairly easily in the morning, are alert and happy for most of the day. Watch out for grouchiness.
Symptoms of sleep deprivation - for whatever reason - in younger children can be mistaken for mild attention deficit hyperactivity disorder(ADHD).
For older children and teenagers, sleep loss just makes them tired and grumpy.
Sound sleep comes with a regular bedtime routine, lots of stimulation during the day and quietening down before bedtime.
Ban the electronic fun late in the day for younger children and have an agreed switch-off time for the teenagers. Reading in bed is fine - it probably won't be for long because sleep will soon overtake them.
As for that bedtime snack, it can be fun but do not overdo it - because children do not suffer from "night-time starvation" And, by the way, neither do adults. It's a myth.
Professor Jim Horne runs the sleep research centre at Loughborough university. More about sleep can be found in his new book Sleepfaring pound;14.98 (Oxford University Press)