I’ve had an electric car since 2011. The battery looks like it will last another 10 years.
Early Nissan Leaf batteries degraded relatively quickly (8-10 years) due to poor battery chemistry and no thermal management. Both of these issues have been fixed in all new electric cars (except the new Nissan Leaf which still doesn’t have battery cooling).
Even the old degraded batteries are valuable as static energy storage, and several people are using them as house batteries.
Most of the cost of a battery replacement is the manufacturer markup. There is at least one company making replacement Nissan Leaf batteries for significantly less than Nissan, and they include the latest chemistry and liquid cooling (unlike Nissan who just give you a second hand battery).
Most electric cars today have a 10 year warranty on the battery. Manufacturers wouldn’t be offering that if there was a reasonable chance you would need to replace the battery in that time.