A suggestion for making your battery last: Turn of everything you don't absolutely need, like IR port, printer port, serial port, firewire, you name it. Turn your screen brightness down, and if you're playing from media other than HD, set the sleep timer on your harddisk very short. If only listening, have your screen turned off.
On my 505G with extended battery, running the machine on 25% CPU, screen off, all ports off, harddisk not spinning and using just the PCMCIA slot and CPU, the batteries last nearly 7 hours, as opposed to two with everything on. On my 505LS, the battery lasts 55 minutes with the machine going full speed, but almost 3 hours with screen and HD off, and CPU running at 25% speed.
BTW, you do get some really funny looks when juggling two seemingly identical laptops on an airplane... Good thing noone has yet figured out what wireless ethernet is, I am sure if they knew, I wouldn't be allowed to use it.
Niels.