for your information:
I just tested my roadpal-store refurbished iriver and did a WAVPACK-recording (lossless packed format like FLAC) on line-in from radio.
After 10,5hours the battery was gone.
It seems WAVPACK makes about 2.5 hours more than WAV(8 hours).
The 2GB limit(gapless new file starts) is at 5 hours when using wavpack(3h23min when using WAV).
I used the REP from July 23rd 2007.