No, it won't lose effect. The longer you sleep the longer your REM stage of sleep (the opportune time to LD) increase in length making it easier to enter into one, this being one of the benefits of WBTB. Check out a tutorial, but basically you want to sleep for 6hrs+ before you wake up to maximize results. Read read read, You can find so much info. On this site. Check out the WILD subtopic under attaining lucidity.