If you count the swap done just before my delivery, I have had 3 replacements, and am on my 4th 12V battery in a little over 2 years.
Let's face it, the current design of the Tesla is really hard on the 12V batteries. The vampire is literally sucking the blood out of them. Every one of those discharge/charge cycles feeding the vampire sucks a little life out of the 12V battery. Suck enough blood (battery cycles), and the 12V battery dies... It used to be worse, but until Tesla tames the vampire load, the MS will continue to eat 12V batteries.
Does Tesla even use temperature compensation for the 12V charge Voltages? For constant use, deep cycle applications, temperature compensation can add greatly to battery life; charge Voltages on a 12V lead-acid battery change -0.3V/10˚C, leading to undercharging in the winter and overcharging in the summer if not compensated.