4 hours of music (and even videos depending on settings) is not a problem for the N810 either. Wesnoth is another issue, from what I've seen it won't ever idle, so your best bet is to turn music/sound off and lower CPU speed (yes, it gets a bit choppier, but can easily double your battery life, especially if you couple it with standard battery tricks like offline mode, lower display brightnes, etc), but don't blame a desktop app's fault on the device/platform.