My 13 year old Volvo has 138,000 miles and the same mileage as advertised when it was first sold. Also, when an engine goes, you can rebuild it, you can do a valve job, or replace the gaskets, replace the oil pump, replace the cylinder sleeves and you have a brand new engine. Or if you have scratches on your cylinder walls, you can bore those out and install wider pistons, rebalance the crankshaft, although on many modern engines the cylinder sleeves are effectively sprayed on and are just a few microns thick, in which case you need to get a machine shop to bore out the lining and install a race sleeve with custom pistons, which is expensive, but you can do it. And you can do this for less than the replacement cost of a car battery, both in terms of price and more importantly in terms of minerals required. You are talking about adding at most a couple of pounds of steel or aluminum versus manufacturing a new 700kg lithium iron with a lot of circuitry.

The main constraint now on car longevity is going to be the circuitry and all the electronic modules. Those expire with time and need to be replaced, and they are the same for EV and ICE, I'd wager that EVs have much more. Thermal stresses, vibrations, capacitors degrade over time, there is corrosion from moisture, etc. How many years do you think all those Tesla boards will last? I would worry about them more than the battery, which has proven to be very durable, and long term we will find ways of servicing these batteries without requiring replacements. Or at least, some manufacturers will, and smart consumers will buy from them. Just think of the problems a 20 year old computer has, one that has been used for an hour a day for 20 years. Now imagine one constantly vibrating, left outside in the sun and rain, etc. What would be the survival rate of that board over 20 years? Not good.

What we all need is an open source car for the electronics, as well as right to repair laws. That is probably the most important thing needed to keep cars on the road.

Not to be that guy, but citation needed. My Pontiac Vibe engine from 2007 worked fine when I got rid of in 2025. Still got about the same fuel economy. My old ass Silverado needed new piston seals but has over 200k miles and still gets 22 mpg on the high way at 70 mph.