Is it possible they just don't like the Texas heat? (serious, not trying to make a joke there).
As mentioned my first one lasted five years, and that was WITH deep-discharging it at least SIX times during the last couple years of its life (which I know is bad for it... each time you let that happen you reduce its ability to take up a full charge again). At the time I didn't see any reason to believe that that battery couldn't have continued on longer, had I not "abused" it with those discharges (which were my fault, not the battery's, due to a current drain problem).
Z-Jay Vice President - Edmonton Z Car Club 93 300ZX TT - Stage VI