Like all encrypted devices, there is a maximum amount of keys it can generate. the yubikey can generate 65k different keys. you only need to use it at the max 3 or 4 times a day. that would give you many years of use. like someone said, you would probably lose it before you used the the keys. If you get close to the max, just order a new one. they are like 25 bucks.. so 25 bucks every 10 years or so (or 20) isnt too bad.. Or, buy 2 or 3 at first, then you would be set for a lifetime...Or 2 or 3 lifetimes..