slow battery problem

I am the only owner of my 94 Jeep Grand Cherokee. About every 2 yrs (between 2 and 2 and 1/2) the battery dies. It happended again yesterday. Other than it's a real pain- I d' sure like to solve the problem. I have replaced the alternator in 2000 and it has died twice since then.

Some notes:
It always dies during the summer.
I have tried many diffrent types MOPAR, Diehard,Everstart.
In the summer the battery volatge as observed on the dash display reads around 12.75v. In the winter about 14 volts.

I know heat can reduce the battery life, but it seems like I have some slow drain on the battery.

Any help would be appreciated