I may be wrong but to my understanding the more dense the luminescent material’s compounds are the longer it will last after being “charged”. It seems like Casio ops for a thin paint or film rather than a cut of material imbedded in the watch like more expensive watches do to either keep costs down or because it’s what’s available to them. Like I said in my other comment though for 100 dollars, I can’t complain too much about this watch as it’s timekeeping is insanely accurate and has a (forged?) carbon core. My work around for low lume duration is a small UV pen light I just keep in my bag, if I ever need to get the hands charged quick or just want to show it off it comes in handy. You can usually find small lights for >$10 at stores like harbor freight.