Some of them managed to sleep for small periods during the rest of the flight.

This will be quite different to their usual routine, of course, when they may sleep for quite long periods.

They slept for periods of several minutes to more than 10 minutes, the researchers said.

The ability to sleep for long periods, rather than the need for sleep, appears to be lost as people get older.

He liked to sleep for longish periods, great swathes of time.

Babies vary in their activity levels, and may even sleep for long periods.

I could sleep for longer periods of time.

Over the first 3 months, the baby gradually sleeps for longer periods.

It also causes them to sleep for unusually long periods of time at night.

And then there are people who simply enjoy sleeping for long periods of time.