You could fit a battery disconnect to isolate the battery when you put it in storage so the various circuits don't drain the battery... You'll lose the radio and any stored info in the computers, but that happens anyway if it drains to flat, but less risk of ruining a battery and more chance of starting it when you return....
aka Jonathan!!
'92 charlotte green auto.... as a daily
'37 Ford Y street rod......... something for the weekend!
...... if a photobucket pic is foggy, click it, and it'll take you to the clear version, yes, it's a clicking faff....