everything is a tradeoff. If your device draws 100mA at 1.5v then the power circuit will pull 107mA when it drops to 1.4v to equal the same power. The lower the voltage goes the more power it will have to draw to make up for it. Of course the more power you draw the faster you deplete the cell.

So there is no way your going to get a huge increase in life.

Noticed they used the worse example, Apple devices are some of the worst WRT battery life coming from the form over function design. Take any other brand of device which is designed better and designed around lower (1.2) voltages and your wireless mouse may last 35 days instead of 30 days on a pair of batteries.

Your still better off buying NiMH