Huh? The above makes no sense. If the capacity drops to where it's "no longer usable", it's not running. ???
My older ThinkPads ran about 3H when new. The current models claim
13H and 24H[*] with the additional "battery slice". These aren't the power "sippers", either (W series). I have no idea how it's measured, though. [*] w/ two 94WH batteries.