It kind of depends on how you define "last" in terms of round life.
If you are talking match grade accuracy the Army Marksmanship Unit pulls barrels every 700 rounds. Most civilian match shooters pull them between 1500 and 2500 rounds.
Insofar as military requirements for a battle rifle production barrels are required to go 6000 rounds at a prescribed firing schedule. The M16A1E1 (adopted as M16A2) was required to go 12,000 rounds by the Marine Corps and they did so firing genuine Belgian SS109 ammo.
I have a sectioned barrel from a gov't test fired at unknown schedule with 20,000 rounds on it and it is missing most of it's chome.
I am aware of a set of M16A1s that were subjected to round counts in the Marine Corps and they all had 40,000 rounds on them.
Acceptance groups for new M16/M4 is 4.5" at 100 yards and rejection is 7.2" at 100 yards with ball ammo. To a match shooter this is not acceptable as they want a barrel that will shoot 1" or less. Thus it depends on your definition of "last".
It it is just gonna be shot at cans etc and not used for match shooting it is a moot point whether it is CM or Stainless.
There is however one barrel I am aware of that should go many thousands of rounds without a drastic degradation of capability. Check out
http://www.superiorbarrels.com/
Especially read the sections on their testing running them in 100 round burst on a M16 lower.
I have three of their barrels and they are IMHO opinion the way to go for long life in a match barrel. It is unknown how long they will last as no one has taken one out yet that I am aware of.
At this time I have five ARs. One is a Colt Pre Ban set up as a NMA2 with 9 twist Delta Elite barrel with about 75 rounds on it. The other is a RRA 24" Varmint EOP that is unfired I have decided to sell as I have not shot it as yet as I know neither of these will last that long as a target grade barrel.
I have one built up as a NMA2 and the others have Daniel Defense 14" 4 rail handguards with 16.5 and 20" barrels. All three are the heavier barrel variety and not the milspec contours. All three uppers were built by them as they have a very unique way of setting them up.
As a rule of thumb the heavier the bullet you use the shorter the barrel life will be.