What I have been finding, is that for about 20 minutes it is REALLY Bright.( after being in the sunlight) then it fades.
It does last through the night ( 10 - 6:30) .
I keep my Rolex & Pan on my night stand, the PAM is much brighter at around 5 am when I wake up for some unknow reason. ( alarm set for 6:20)
