Fully stock, I got about 6-8 hours on a charge. After disabling the DRM service (and doing nothing else - no custom ROMs or kernels), my battery life went up to 20-30 hours.
Now I'm on DK28, and killing off the DRM service seems to have no effect. I'm only getting about 8-12 hours. WTF?
EDIT: I just figured it out. OmaDrmConfigService actually seems OK now. It appears whatever crappy code causes the sleep problems has been moved to the Media Hub service (can't remember the exact name). I stopped that service, and after seeing my battery life go back up and no problems occur, I nuked the Media Hub app from my phone completely. It's all good now!
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Sprint Samsung Epic 4G
Previous PDAs: Handspring Visor Deluxe, Sony CLIE, HP iPAQ h2215
Previous Cell Phones: Motorola E815 (Verizon)
Previous Smartphones: Treo 700p (Verizon), Centro (Sprint), Touch Pro (Sprint)