Originally posted by thedustinI know you meant Powerbook, but by turning off airport when not in use will save battery life. You were gettin' pretty low!
Modern 802.11 chipsets have pretty good sleep modes. Earlier ones do not. Currently, the good ones waste only 5-10mW while asleep, and they tend to operate at 3.3V. (some 1.8V!) Accounting for the conversion loss, that means that a good 802.11 module will be able to run alone on a PBG4 battery for about 7000 hours, which is the equivalent to nearly 300 days.
THe airport extreme is a little worse on power, but even if it's 5 times worse (which is about right), that's still 60 days. You can do much better for yourself by dimming the display.