If that's the case, how can they claim 20hr runtime. Sometime after the 11th hour on your graph, I would consider it spent. To me at least, if they claim 20 hr runtime, that shouldn't include faintly glowing time as well. It (their ad copy) is very misleading to the public, IMHO. The photocell and graph tell no lies. I can only make that statement based on my exp. with this light as well. I do NOT get 20hr of "useful" runtime with mine. Don't get me wrong, the light is built like a sherman tank, and for that it has its merits, but the specs needs to be more realistic.