>> At 20 years in and 12,000 miles per year, 240,000 miles, they'll quite likely have 85% of their capacity
Not even close, especially in hot climates like CA and AZ. I used to work for one of the 3 big EV charging station companies and they also have a sister company that does EV battery testing for the government. I can tell you that no EV car battery lasts anything like 20 years. With a normal drive cycle its about 4 years max before you start noticing very significant amounts of dropoff (like 1/3) in max range, and depending on how determined to save money you are, it will be maybe 7-8 years max before even the most determined owner HAS to totally replace the battery.
Tesla is also using the same battery tech as everyone else so they are just as susceptible, no matter what their glossy advertising claims.
This is demonstrably false, as Teslas have been out for more than 4 years and are seeing minimal battery degradation. I have a 2012 Telsa (one of the first 2000 off the line) and the battery degradation is sitting at 96% of its original capacity. It has almost 100,000 miles on it. So I've lost 4% in 4 years and it's been holding steady for the past year at that rate. There are numerous other examples of this in the Tesla world. Do your research. Spewing false facts (ahem, I mean alternative facts) about EV batteries isn't helpful.