From one of the Israeli pilots who helped prevent Iraq from getting nukes:
Today, Israel sees the prospect of a nuclear Iran that calls for our annihilation as an existential threat. An Israeli strike against Iran would be a last resort, if all else failed to persuade Iran to abandon its nuclear weapons program. That moment of decision will occur when Iran is on the verge of shielding its nuclear facilities from a successful attack — what Israel’s leaders have called the “zone of immunity.”
Some experts oppose an attack because they claim that even a successful strike would, at best, delay Iran’s nuclear program for only a short time. But their analysis is faulty. Today, almost any industrialized country can produce a nuclear weapon in four to five years — hence any successful strike would achieve a delay of only a few years.
Full commentary here.