Thanks guys, I don't know what you did, but after upgrading my laptop FC17->FC18 I saw a 5 hr battery life being quoted - I never saw that long before.
It may be something to do with optimus? My nvidia video card is not working inF18 as there is no bumblebee rpm yet, but maybe someone worked out how to switch it off by default? (suits me). Anyway, I'm happy! Bill