Obviously getting a long warranty or a longer-than-warranty battery life would be great, but I tend to look at this issue differently. I figure that with the incentives, I'm getting a $32K car for $25K. So after five years let's assume there is no more battery warranty. Chances are my battery will last well past that, as pointed out earlier in the thread, since I drive low mileage. This means no problem, and it's still a bargain. If the battery fails right before the warranty is up, I'll probably get a brand new improved battery with greater range and life, if battery technology improves as we expect, although Nissan may pro-rate the battery the way regular car batteries are now, but my guess is they'll just give me a new one. Still no problem and it's a good deal. Worst case, after five years the battery fails and I have to buy a new one. By then, again, probably I'll get a better battery with longer range and longer life. So it will probably be a 7-year or more battery, and cost, say $7k. That means I've spent $32K on the car - what it was worth in the first place - and deferred $7k of that, and have a better car (due to longer range from the new battery) that will last a total of 12 years, a good long life expectancy for a car of that value, and of course even then, there will probably be even better batteries available to extend life even further if the rest of the car is in decent shape. In the meantime I've spent much less on repairs and fuel than I would have on an ICE car. Still a good deal in my book. I see it as no-lose.
