$29K buys a lot of gasoline.

More often than you think. EV lovers keep saying you have 80% capacity after a certain amount of years, but they don't realize that means 20% less range. When something like a base Nissan Leaf gets 168 miles on fresh batteries, losing 20% of capacity means it's only 134 mile range. And that's from full to empty, with no heater, stereo, etc. And it's not like you can drive it 130 miles and pull into a charging station and be on your way in 5 minutes like with petrol.

It's just like a phone, eventually it stops having the battery to do what you need it to do, so you get a new one or replace the battery before the phone needs to actually be replaced. Yeah, it's easy to say it's no big deal, battery is at 80% capacity, but on a phone that could be the difference between making it through the day and not. And in an electric vehicle, it could be the difference between making it back and forth between work or not.

My understanding is roughly every 10 years depending on the battery manufacturer.

If you buy a Tesla today, they say that you should expect to swap it out after 8 years. That is when the batteries have lost 20% of their range.

Seeing how Teslas are mainly commuter cars, if you use it for anything other than short hops to work and home, never allowing the battery to discharge less than 50% Then you'll get the 8 years.

But if you drive it until the charge drop below 50%, or use it for more than just daily commuting, or (and this is the big one) if your car is routinely exposed to freezing temps, it'll be far less than 8 years. And battery tech has improved over the years. Get a Tesla that's a few years old and it'll be far less.