I didn't fly for approx. 10 days and two of my fully charged batteries lost approx. 40% of their charge*

Is that rate of drain normal?

* please no battery police telling me it's not good to store fully charged. Wasn't planning to not fly for so long :-)

Yes, this is normal ... Please read manual ;-) ... Battery is automatically draining when not used after x days..

Definitely read the manual. i usually never do for anything but for drones its a must.!!!

Hmm ok i must have missed that - will revisit. Damn i hate to be that guy who needs to read the manual but fair

Yeah its clearly stated in the manual - If you do not use the batteries for 10 days they begin to do a slow drain to a safe level for battery health. The manual also notes that the batteries may feel warm during this process