Leaf batteries ~ life span & replcmnt cost?

Using the Leaf as an example; what is the current estimation for how long its batteries will last and how much will it cost to replace them? I know such estimates are approximate considering how quickly advances are being made in this area.

Thanks!

I asked a sales person at a Nissan dealer and they said the batteries are guaranteed for 100,000 miles, when I asked how much to replace the batteries they said it cost $5000

I know he was way off on the $5000 guess to replace the batteries,

there is some kind of 100,000 mile guarantee on the batteries, because several people have mentioned it, but I have never seen anything in writing so who knows what the guarantee actually is.