Just adding that I am experiencing this too with my FP5.
So far it hasn’t annoyed me. In my case sometimes it’s helpful as I often leave the flashlight on by the bed, and it turns itself off after some time. (And I thought it was some sort of energy saving feature.)
But I can see that turning itself off could be annoying in other cases.
In any case, wanted to also share my experience. Hope this is fixed though.