I think my "Lombard" or maybe "Pismo" powerpc powerbook did longer than 3 by far. And my iBook would go 8 hours no sweat.

edit: fixed the nickname

Mine managed 6-8 without too much problem throughout the time I was in university. And they had removable batteries so you could just switch them out if you ever needed to (I had two for my Powerbook, and that would do a full day on campus without ever having to go near a power outlet).

G4 ibooks were crazy good for battery life, I often did a whole day of uni on my little white beast.