REM cycles, dream length, DEILD

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 :)?

THat's sort of what I reckoned was happening with my WILD attempts. I would wake either at the beginning, middle or end of a REM period, but I think waking sort of "reset" the cycle so in order to LD I had to wait til the next REM cycle came round.

These are a series of excellent questions! Perhaps some regular DEILD'ers can chime in. My thought when I am able to DEILD is that it has to be the same REM cycle because it all happens very quickly...it starts with my dream fading, then becoming aware of my waking body lying in bed usually accompanied by vibrations, then back into a dream.