I'm not saying it tops it up above the threshold.
Lead acid batteries don't like being deep discharged. Let's assume Tesla has set the threshold for "wake up specifically to charge the 12v" when it reaches 60% capacity (conventional wisdom is that 50% or below causes irreperable damage, so it's probably more like 70% or more). In the case of my car, not being driven for several days or even weeks, it is getting to that point, waking up, then spending 1-3 hours (usually more like 2-3) recharging it back to 100%.
Now imagine that instead you're driving the car every other day. When the car is awake, at all - including just being sat there with Sentry on - it is maintaining the 12v battery - which is to say, like an alternator, it is giving it ~14.5v+. You can confirm this by going to Service Mode and seeing that the PCS is doing this ("Support Status: Active") when you're sat in the car.
In the scenario where the car is being driven every other day the LV battery is never hitting 60% (or whatever the wake threshold is) because it's never sat there idle for long enough. This means the LV battery is healthier, requires replacement less often, etc.
That I can certainly agree with.
I was hoping that if I ran the kits off an auxiliary battery, then I could at least protect the main car 12v from discharging. It sounds like quite a faff though.
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