MM Pro enough for a savage?

[scarletboa]

what is the difference between the v3 and v4 mambas? if i get a MMM right now, it'll be a v3 and not the newer v4. will there be the same policy with the v3s that there was with the v 1 and 2? if my v3 were to fail, say, 14 months after i get it, would i be able to exchange it for the current model? or was that only with the v1 and v2 due to the high failure rate?