Hoosier,
Two quick points here; #1 is that no, moly doesn't extend barrel life. Friction, which is to some extent allieviated by the use of moly, isn't what washes out barrels. It's high temperatures and pressure that erodes the throat, and causes the loss of accuracy. Moly doesn't do anything to change that part of the equation, so you're back to square one. And #2, twist doesn't directly play a role in barrel wear, but it's easy to see where that assumption could be made. Generally, fast twist barrles wash out faster than slow twist barrels, but it's not the twist rate that creates the differences; it's the bullet weight. Fast twist barrels are generally chosen when the shooter wants to use the rifle with heavier bullets for a given caliber, and slower twists limit the shooter to the use of relatively light bullets. It's the bullet weight that creates the problem here, and it's all about inertia. Simply put, it takes a bit longer to get that long, heavy bullet moving down the bore than it does a short, lightweight projectile in the same bore size. That extra time is what allows the heat and pressure to play havoc in the throat area, beofe things start to move on down the bore. A quick peek in any high mileage barrel will show you the same thing; an area just ahead of the chamber that is cracked, pitted and fissured, and the remainder of the barrel appearing to be nearly pristine.
I've repeated this in literally hundreds of barrels in at least a dozen different calibers, and thre trend is exactly the same in all of them. Light bullets, longer bore life, heavier bullets, shorter barrel life. That's the cost of doing business if you need the higher BC and SD provided by those heavyweights.