No person shall be elected to the office of the President more than twice, and no person who has held the office of President, or acted as President, for more than two years of a term to which some other person was elected President shall be elected to the office of the President more than once.
If some termination to the services of the chief magistrate be not fixed by the Constitution or supplied in practice, his office, nominally for years, will in fact become for life; and history shows how easily that degenerates into an inheritance. Believing that a representative government, responsible at short periods of election, is that which produces the greatest sum of happiness to mankind, I feel it a duty to do no act which shall essentially impair that principle; and I should unwillingly be the person who, disregarding the sound precedent set by an illustrious predecessor, should furnish the first example of prolongation beyond the second term of office. (Reply to the Legislature of Vermont, 1807. ME 16:293)
Although it is indeed frustrating to see a great leader - whatever one's definition of such may be - refused the opportunity to lead, simply because he has spent what has been defined as "too much" time in office, the current administration of George W. Bush provides ample illustration of why the 22nd Amendment is a good thing: No amount of dirty tricks or fear-mongering or outright cheating can put George W. Bush back in the Oval Office. He can't even run for president, and for that - as the video reminds below reminds us - we should be eternally grateful to Ol' Number 22.
["22nd Amendment" from Andrew Sloat on Vimeo]