Since when do petrol and Diesel cars last more than a Million miles. Modern Batteries will last a lot longer than 150,000 miles.
Like any battery it will degrade overtime. Manufacturers battery warranties, guaranteeing an acceptable battery capacity of at least 70% of the original specification after seven or eight years. Like an ICE vehicle the bettery you look after it the better – a battery that has spent its time being trickle charged will degrade less than one that has spent its charging life on fast chargers. Also some battey chemistries are better than others. Yes its credible a diesel car is capable of a million miles if looked after however its less epensive to repair an ICE engine out of warranty, than it would a battery.
High Voltage warranties are 8 years and cover anything between 80,000 and 100,000 miles. That’s everything from the charging port to the motor that carries high voltage, which is a lot more than just a battery. It also doesn’t mean that at 8 years and a month the battery collapses into a state of disrepair and needs complete replacement.
Currently costs for replacements aren’t cheap, however, I’m pretty sure that the cost of an engine replacement isn’t that good either. What will come, in time, is the ability for cell replacement in battery packs, renewing faulty cells rather than the entire battery for a cost more like replacing part of an engine over the whole unit.
I'm Autistic, if I say something you find offensive, please let me know, I can guarantee it was unintentional.
I'll try to give my honest opinion but am always open to learning.
Mark