Most batteries won't let you completely drain them. In fact, draining them completely will ruin them.
They have built-in circuitry to prevent that from happening. The battery pack is made of multiple cells, and one cell will always go dead before the others. If you try to drain the battery pack, the first cell to be drained will end up having a reverse voltage applied, which is somewhat less than healthy.
Lithium ion or NiMH batteries don't suffer from the memory effect that the much older NiCAD batteries do, so don't need to be drained.
NiMH battery life is more a number of charge/discharge cycles, so they shouldn't be recharged too soon for maximum life.
Lithium ion life is dependent more on the age of the battery than the number of charge/discharge cycles, and it won't hurt them to be recharged when only partialy discharged.
The main reason to "Drain the battery completely" is to re-calibrate the monitor that tells you how much life is left in the battery.
You can change the power settings so the system goes into standby/hibernate at a lower percentage of remaining battery life.
Control Panel | Power Options
Change plan settings
Change advanced power settings
At the bottom, several options under Battery.
Make sure the Low battery action is do nothing
Set the Critical battery level to 3-5%
Set the Critical battery action to shut down/hibernate, instead of sleep.
You may have to change BIOS settings as well.