I had to replace my '95 battery at 33,000 miles, in 1999 (under warranty). It quit cranking the car rather suddenly, despite what someone else said (but this is obviously on a daily driver). I had one warning of batter trouble about two weeks prior to it leaving me stranded at a restaraunt. The second battery (stock mopar) lasted past 65,000 miles and three years.
While I agree that its not something you just want to replace for no reason, I do agree that a battery WILL die eventually. Just when it dies is something you can't predict.