The only real problem with disconnecting the battery while you are gone for months at a time is that you feel pretty silly when you get dropped off at the car and jump in, pull the key out of its hiding place and give it a twist and NOTHING HAPPENS......
So, you say a quite Oh-5h1t to yourself and pluck the 13mm wrench out of the console where you stowed it. Then you trip the hood release and go out and open the hood, stuff the negative cable back on the post and snug the clamp. Then, you slam the hood and start the car....
This never happened to me, but I heard about it several times....
Matt