whats a good battery to buy?

If you leave a battery hooked up for 2 months & just sitting it is going to go dead. if the car sits, unhook the negative cable. Cranking it every so often isn't going to help you out either as cranking just drains the battery more. I love the optima batteries, I have them in all my cars. (best thing about them, it they don't leak acid). I suppose you might have gotten bad batteries but I would have to say you have the worst luck in the world lol. Ask whoever checked your car out if they did a parasitic draw test. If not , have one done. I would almost be willing to bet that you may find a problem there. Best of luck to you with your concern.