just got up from my nap
I got up at 5:00 am today, went to bed at 11:45 pm and had a nap today from 6:45 pm to 7:30 pm.
My earliest wake up time I can handle without negative consequences (tiredness, lack of concentration) is around 4:30 am with a minimum 60 minute nap. This makes a total of around 5.5 hours total time in bed. If you take into account that you have to fall asleep twice instead of once so you lose some time there - I think that's pretty good and realistic.
My next goal is 4 hours a night plus the nap (60 to 90 minutes). I don't want to ruin my health and my limit is when it doesn't feel right anymore. I have extremley low cholesterol levels because of my nutrition, I workout - not in the gym but with bodyweight training - and I actually find it pretty strange if someone out of shape who is drinking alcohol, smoking and eating lots of (trans)fats complains about my "unhealthy" way of living.
For me it's the quality, not the quantity. I am no walking zombie at all. I feel better now than I did with my standard 7.5 hours of sleep. I enjoy the reboot in the evening because after my nap it feels like a whole new day. Sometimes I start my nap stressed out because of my work and not feeling like doing anymore that day and wake up ready to conquer the day (or evening) again.
I never really tried polyphasic sleep but bi-phasic really does it for me.