The iBook sleep lifes are phenominal. My 800 G3 would get almost three weeks in sleep (though those were rare stretches of time). The current PB I'm using seems to lose about 2-3% in an 8 hour span.
ITASOR, only 3.5 hours? My old 800 G3 iBook pulled 6 hours of life on a battery charge only a few weeks before I sold it earlier this month. I was doing some basic Photoshop work and had Airport running the entire time. Even from the beginning, I had been impressed with that 14" iBook's performance. The battery life is something I'll miss.