With an 1100-mAh battery, the Dell Axim x50v runs its graphics core at around 67-MHz (maybe up to 75-MHz) with a 624-MHz Intel ARM XScale CPU and a 640x480 display to rate at about 4.5 hours of continuous play at full stress.
No way.
The Axim x50v run with the normal 1100 mAh battery at full stress 2 hours. I have tried it yesterday evening with full speed running my earthbench in a new not published version.
A lot of that depends on the screen brightness, if you decrease it your battery will last longer... these days LCDs are probably the biggest battery users of a PDA, closely followed by wireless network.
Battery life shouldn't be quoted IMO with "full stress" in the same sentence; not that much different with laptops either.
Fine if I let the laptop sit there doing nothing and the screen switching off after 10 minutes I wouldn't be surprised, if it would reach the maximum claimed battery life.