[BlueMondaySkipper]

The reason hardware makers use batts that can only be replaced in-factory is to increase the time between charges, thus the 17" MacBook Pro lasts a long time on a charge.

At least on the surface, that make absolutely no sense. The batteries used for a device and not the process required to replace them determines how long they last per charge. The process to replace them simply changes the convenience/cost.

[SunkenCiv]

Nope. The connectors and other space-eaters needed for user-replaceable batteries mean smaller batteries.