I was reading a discussion on another part of the internet and many of the people involved asserted that it was common to use the phrase "go to bed" for "cease all other activity and go to sleep" even if the speaker were already in bed.
For instance someone might be in bed, under the covers, reading a book. They would close the book and say "I'm going to bed now".
In fact some people expressed surprise at others' not knowing this use of the phrase.
Is this use of "go to bed" common in American, Canadian or some other variant of English? I believe most of the people familiar with it were north american speakers.