I have a '92 with about 80,000 miles and its original battery. I had no problems with the battery until this winter. I live in the Washington, DC area and this year we've had colder than normal temperatures.
My battery finally failed to start one cold morning, but then worked okay a day later when it got a little warmer (near freezing).
I was able to get the car started by jump starting it, but it wouldn't hold a charge. I figured that after 11.5 years it was finally time to get a new battery (I don't have a charger, or I would have tried charging it). Surprisingly, my local dealer (Rosenthal Mazda in Tysons Corner) has the best price on batteries, including WestCos.
I took my old battery out of the car and let it thaw out in my house for a couple days. I got no voltage reading when I tested it with my multimeter (as described in the Enthusast's Manual). After a couple of days I put it back in the car, and it started right up. The temperature has been in the 20's the whole time, but it works fine again.
I guess it wasn't dead after all, it was just hibernating :)
-Jeff Buck