Thread: wbtb question

Hey guys, quick question....
They say when u do wbtb, it should be 4.5 hours, or 6, or 7.5 hours after sleep....
I always wake up after 3 hours or so....no matter what time I go to bed, I always wake up
3 hours later. I have always been doing my wbtb method like this, and I've been pretty
Successful with it.
My question is, I've hit a dry spell recently, so should I try to sleep for 4.5 hours and wbtb?
If I wake up after 3 hours, then try to go right back to sleep immediately to get in the extra 90
minutes, will I throw my cycles off?
As a side note, I hardly ever sleep for a full 8 hours on any night, ever....mostly 6 or 7....