Is there a theoretical maximum dream length? I mean the time spent physically asleep and dreaming between (even short) wakings. Is the maximum equal to the length of the REM period? Do we *always* wake up (even a micro waking that we mostly don't notice) after a REM cycle finishes and the next NREM starts? Or during the course of one REM period, do we always have little awakenings after (some number?) of minutes?

For those experts who DEILD frequently with a high success rate: does DEILD only work while within a single REM cycle where you can get instantly back to thet same REM sleep? Do DEILD attempts fail when the waking occurs at the end of a REM cycle (because there is no REM left to enter)? Does anybody actually know this ?