Part of what's so confusing about all this is that so many people declare, with such conviction, such contradictory things, in various forum threads and websites:
"Stay around 50%. No, drain the battery down to 20-30% and then charge to 80%. Charge to 100%. Charge to 80%. It doesn't really matter if you charge to 100%. It does really matter if you charge to 100%. Charge to 100%, but make sure you jump in the car immediately and start driving. Charge to 100%, and it's fine to leave it that way for a day or two. Here's a chart. Here's a different chart. Quick charge is bad for the battery. Quick charge is fine, I do it all the time, and I haven't dropped a battery bar yet. Just drive the way you want to drive, and don't get too hung up on the details. Get hung up on the details or your battery will degrade quickly, and since they now cost $8500 to replace, you're hosed."
I don't mean to sound ungrateful; I genuinely appreciate all the advice I've gotten here, and all the posts I've read. It's just hard to know what to make of all the advice when you're a noob. Personally, I've observed that my battery SOH seems to improve when I drive longer distances at a time, counterintuitive as that seems, and also when I do a deeper discharge and then recharge, like from 30% to 80% instead of 40% to 60% -- but this is from LeafSpy, and apparently the SOH readings tend not to be reliable over short periods of time, so that observation may be totally wrong. And I've only had my car for a couple of months (2013 SV, 11 bars but dropping to 10 any minute now, non-lizard battery).
I have no idea how everyone came to their recommendations. It's possible that no one really knows for sure, and since people's experiences are different, their advice is different. The only things people seem to mostly agree on are:
1. L1 and L2 charging keeps the battery cooler, which is good. Quick charge (L3) only when necessary.
2. Heat isn't great for the battery.
3. Driving faster drains the battery faster.
4. Drive gently to extend range.
Right now, what I'm doing is charging to 80%, driving for a few days until I hit the low battery warning (at a little over 30%), and then recharging to 80%, typically at night when temps are at their coolest. I'm collecting data as I do that, mostly about miles driven and SOC, which seem to be the most solid numbers. I may then try the same thing charging to 100%, and compare data.
I did try charging a bit each day and keeping the battery between 40% and 60%, but the SOH did not seem to like that -- which, again, might be meaningless over such a short period of time.