Is there a time limit for staying in a LD?

Is there a time limit for staying in a LD? What I mean is after getting lucid, and stabilizingthe dream, do I take a chance on forgetting the dream if I stay there till I naturally wake up? What happens if the REM phase ends and I remained in the lucid dream? Do I get into deep sleep and forget about the dream? Is it preferable to wake up after say...10 minutes or 20 or 30?

You will naturally wake up once the REM period is over, so not taking into account time dilation stuffz, you could have dreams as long as 1 or so hours, and if sleep deprived, maybe up to 3 hours.