Since buying a couple of OEM compatible batteries, I noticed my original battery seldom sees service and has been left in the bag for a few months with zero charge.

I hear that leaving a battery for long periods without any charge shortens the lifespan. If this is true, what would be a good percentage charge to store batteries? I think it's about 70% for laptop batteries. Same for camera batteries? (Btw its a Canon LPE5 Li-ionCanon 7.4V 1080 mAh)