I actually did a little experiment on this awhile ago. I deprived myself from sleep for 80 or so hours. As I was getting ready to go to bed, I wrote down what time it was. 23:00. I also recited a mantra and told myself I would wake up as soon as a dream ended. I used the WILD technique and went straight into a dream. The dream eventually faded out so I woke myself up. I woke up at around 2:30AM.

Quote Originally Posted by SilverBullet
People are stating the regular REM cycles, as if they completely dictate what happens when you sleep.
I myself have experienced almost 2 and a half hours of pure rem sleep with a WILD in the morning a couple of times.
I fell asleep and immediately entered a lucid dream. The lucid lasted a long time, when it ended I woke up, a little over 2 hours later.
From my experience, with lucid dreaming you can force REM sleep, but your body only needs around 2 hours of REM sleep total. So that might be when I hit the possible limit. I woke up feeling like I slept for a LONG time. You might be able to force yourself to go longer than that.
I agree with what Bullet said. Even though I ended up with around three and a half hours of REM sleep, I believe if you were more experienced you could force it to go much longer. A friend of mine told me he was in a dream for 6 hours, but I'm not sure about that, as he may have just linked multiple dreams together. I know for sure with practice and sleep deprivation you can get at least three hours straight. If someone with more experience wants to try it out, by all means go for it.