Well, I don't.
Maybe I do, anyhow, it feels very short, but I can't complain because there are so much options in rockbox that I almost never just play songs. about a week ago I've made a serious battery test playing on the iriver firmware an mp3 directory coded at about 112~128 kbps, the battery lasted for more then 16 hours, and i've had the player for about two years now (!)