Quick followup on day 354: it's been at 3.07 volts ever since, and I realized: in the days leading up to day 350, I'd been wearing a different watch to test some firmware changes. As a result, the steel watch had been sitting at room temperature for about a week — not warmed up to 90° F by my wrist. Lower temperature, lower voltage? Anyway it'll be a few weeks to months before I'm sure, but I think we're still at the top of the discharge curve; I don't think it's started curving just yet.