fukdane, the most I have got out of mine - constantplay, switching cds as little as possible - is about 7 hours. 6 hours and its down there near empty for the most part.
With the battery back, I got about 15 hours from mine.
I've no idea if this is true or not, but a Japanese friend told me that he heard a 3 month forecast that said there would be more snow than average in November. Do they usually forecast so far ahead?