I have researched this and read several blogs by people who maintained various sleep schedules for long periods of time.

The indications suggest that your body needs considerable time (3-7 weeks) to adapt to a different schedule. During this stage your body learns to enter REM at a different time and at different speeds. For example, in one blog the guy was going 20 minute naps every few hours. He did this successfully for about a year.

After passing an extremely difficult period of about 4 weeks, if I remember correctly, he adapted to falling asleep instantly and going straight to REM. Basically his body learned how to immediately start REM sleep by shortening the entire sleep cycle. After he stopped he still found that he would enter REM within seconds of lying down to sleep (this "skill" appears to be permanent for him).

Doing your experiment the way you are, I think you are wasting your time unless you pick a schedule and stick with it for at least 3 weeks without "cheating". Some schedules need much less adaptation than others, depending on how much they vary from the regular monophasic sleep we are used to and how much total sleep they give you (the triphasic one where you do 3 ~90 minute naps every day is the easiest). For more detailed information on various schedules and the best way to adapt to them check out this site:

Sleep Schedule Overviews | Polyphasic Society