If you "rockbox" the clip+, that would offer the biggest improvement in terms of battery life over using the stock Sansa firmware. You should get over 10+ hours as the FLAC encoder is implemented more efficiently on the rockbox firmware.

http://www.rockbox.org/wiki/WhyRockbox

http://www.rockbox.org/wiki/SansaRuntime

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne