The life and proper use of NiCads is so well known, that we take it for granted. The LiFe batteries will become that way; as well, as we use them more and more. They just have a different set of rules to follow. I think their done when they will only discharge to 80% of capacity just like any other battery. As for catastrophic in flight failures; who knows how that's going to pan out in the long run. I suspect junking them every 2-3 years is your best bet to avoid failures. I would also cycle them every 3 month or so to check capacity.