ON top of everything else, DRM sucks down additional battery power:

When it comes to the Creative Zen Vision:M's 14-hour claim, CNET got about 16 hours of playback time with MP3s from a full charge, which was a nice surprise. However, when they tried playing WMA 10 DRM crippled subscription tracks on it, they only got just over 12 hours; a loss of almost 4 hours (~25%) of playback time due to the battery-hungry DRM. CNET found similar results with other players with WMA DRM drastically reducing battery life by up to around 20%. Apple's FairPlay DRM seems to have less of an effect with battery life being reduced by around 8% when compared with MP3 playback.

The upshot:

When it comes to maximising battery life in a portable MP3 player, this is a clear sign that one should avoid playing DRM protected music if at all possible and also another good reason to get the music converted into a more battery-friendly format. While 2 to 4 hours may not seem a lot to some people, this can be the difference between listening to music to the end of a lengthy journey or getting left in silence a couple of hours before the journey is complete.

That's the RIAA for you, insisting on technology that drives you to find ways around it. That piracy they see? Like Dave Winer, they need a mirror to ponder the answer.