My 2012 MacBook Pro needs a new battery. It’s going to cost over $500 to replace—½ parts, ½ labor. It turns out I could've made the battery last longer had I known how to properly care for it.
With older style batteries (NiCad and NiMH), it was beneficial to completely discharge the battery before recharging due to “battery memory”. However for modern lithium-ion batteries (Li-Ion), the reverse is true.
It’s best to keep your batteries charged as much as possible, top them off whenever you can, and keep your devices plugged in as much possible.
Coconut Battery is a great little utility for your Mac to view detailed battery diagnostics.