To answer your question, the longer I sleep the more I LD. If I get about 12 hours of sleep in a night, I will almost 100% surely have an LD. It usually occurs in my last 2 hours of sleep. My body and mind are reenergized and I don't need much more rejuvenating deep sleep so I REM almost the entire time. I think because the mind is rejuvenated at this point it becomes more aware and dreams become more vivid and memorable during this period. So this is the best chance to LD. Ever notice how if you take a nap in the afternoon after having had a good night's sleep that you almost always fall right into REM? That's because your mind recognizes you don't need any regenerative sleep so it sets you into REM.

I recommend getting 9-10 hours sleep minimum for optimal LD conditions. If you can get to bed early enough, do 12. If you can't sleep for 12 hours because you can't fall back to sleep, try what I do sometimes. I'll sleep 3-4 hours, then I'll get up and take a sleeping pill (Melatonin, Unisom) and go back to sleep. The pill should be active for the usual 8 hours, so it extends my ability to sleep.

...Sweet, it's my Blink 182nd post on DV