No battery lasts for ever as you know. Failure to hold a charge may mean its ready for disposal. My battery is shot, so the laptop runs from the mains power supply unit, but the battery stays in the circuit..
Adjust the screen brightness. Use any power saving software that came with the laptop.
Some tasks are much more power hungry than others, don't keep unused programs open.
I wait till the little window comes up and tells me that it is empty. then I charge it with the plug. sorry I'm not technical that's why I have to explain like this !