I think the "battery exercise" is simply not having them sit at zero charge or 100% charge for too long. A few hours at 60% SoC until the sun comes up and fills them up again having them sit for a few hours at 100% while your solar is running the house isn't that big of a deal. And we've learned that if our App says a Powerwall is at 100%, it's really only about 90% as a concentration of potential energy stored in the cells. I guess Tesla is basically making it mostly idiot proof to damage your powerwalls when using them with the provided options.
Personally, with the way the smoke and BS in the sky is so unpredictable, I want the highest percent chance I can get my powerwalls back to 100% charge before peak time. Sometimes I hit the 100% charge by noon... sometimes it only gets to 95%. But in every instance, the moment off-peak comes around, I want to take power from PG&E since that is the most efficient approach at this time.
If/when PG&E starts charging a fee to export solar energy to their grid, 2 things will happen.
1) I will laugh at
@h2ofun
2) I will look into more Powerwalls
3) I will look into more disconnects
But I still think the best approach is to use Grid power once off-peak rolls around.