There's over a decade of real-world data available from Tesla and Leaf, and the batteries are very long-lived: they degrade about 1%-2% per year with a good battery management system, and around 3% per year with Leaf's weaksauce one.
Additionally, batteries are getting cheaper and more energy dense, so when it's time to replace them, you'll probably get an upgrade for cheaper. Leaf started with 24kWh batteries, and now you get 40kWh for the same price, and a 64kWh upgrade option.
People often extrapolate from their experience with cell phone batteries, but these "lithium" and those "lithium" batteries are very different. There are different chemistries, different conditioning with active cooling/heating, different rates of discharge, and a big difference in redundancy when you have 1 cell vs 7000 of them.
Additionally, batteries are getting cheaper and more energy dense, so when it's time to replace them, you'll probably get an upgrade for cheaper. Leaf started with 24kWh batteries, and now you get 40kWh for the same price, and a 64kWh upgrade option.
People often extrapolate from their experience with cell phone batteries, but these "lithium" and those "lithium" batteries are very different. There are different chemistries, different conditioning with active cooling/heating, different rates of discharge, and a big difference in redundancy when you have 1 cell vs 7000 of them.