Either Iran could build a nuclear bomb in a matter of months or it is unlikely to get such a weapon any time soon -- depending on which Western expert you talk to.
The differing estimates show the difficulty in trying to assess how long it could take Iran to convert its growing uranium stockpile into weapons-grade material and how advanced it may be in other areas vital for any bomb bid.
The discussion is as if we might do something about it if Iran was really close. Please. There will always be reasons to doubt how close Iran is until they detonate a test bomb to prove they have the technology. There will always be alternatives to the "last resort" of force.
It is pointless to discuss how long it will take Iran to go nuclear as if that is a major problem of deciding what to do. I think the discussion is just a way of justifying doing nothing.
We need to decide that Iran under the mullahs should not have nuclear weapons. Do that and determining precisely where on the path to nuclear weapons Iran is becomes obviously pointless. The decision is then what to do about Iran.
Unless you really believe it is vitally important to know whether Iran is a nuclear threat in a matter of months or years. And if you think Iran can't figure out why it is important to know that.
Have a nice day.