Sleep mode takes 6% of the charge every 15 hours, takes a lot of data to see that happen tho. The PD is always unplugged from the headphones if not in use. And no, what I meant was, that VERY FIRST TIME you charged, did it play as long as it does now? Can it be remembered? Also, I'm pretty sure in keeping mine forever and will use this till it's totally dead, which I hope it's more than 4 years.