Free: Contests & Raffles.
Most cameras I keep the batteries in and have never had an issue over time and with tons of cameras. However, my 7D2 drains the battery for some reason. I'm told that even when you turn it off the gps is still running. Either way, I have to pull the batter on just that cam. You can leave cards in your camera forever with no issues.
I've noticed that the Kirkland brand batteries seem to leak in just about everything I use them in for some reason. My LED flashlights and headlamps being the worst culprits. I bought a couple new cams this year and put the lithium ones in them. I'm hoping that they don't leak cause I'd like to keep them out through the winter this year.