I think it really depends on how people use their cars and how they take care of their batterypacks.
In most cases I have read, where the batterypack needed replacing, was with people who drive a lot of KM's and use the Super charger pretty much every day.
Fast charging any batterypack that often is really bad for longetivity and will shorten the lifespan of the batterypack.
Also charging to 100% often will increase degradation as well.
Li-Ion batteries in general can't handle 100% and below 10% levels for long periods. This will ruin the battery.
Best way to use the car is to keep the batterypack between 30 and 70-80% on your daily commutes.
Only charge to 100% on the start of a long trip and then try to keep the batterypack between 20 and 80% on these long trips.
It's better and more efficient to stop and charge more often on a long trip anyway, since charging below 20% above 80% is incredibly slow.
If you follow those recommendations, then your batterypack should last a long time without issues. Unless you are just unlucky with a fault in the pack.