...As far as the plunger tube, if they're not staked correctly, they can come loose. Plunger tubes that are staked correctly should be good for the life of the pistol. A failed plunger tube is not a fault in the design, but a fault in assembly...
I disagree. "Staking" is the process of plastic deformation of the soft steel. If the area that is staked is very small as in the plunger tube, I would expect the small amount of metal that is involved to become battered and loose its shape after a high round-count even though the tube would not seem to be put under that much stress during the firing cycle.
It was a common occurrence in the pre-milled cut for the front sight days, for any replacement sight with more mass than the original "quarter moon" to shoot loose if staked in the original hole in the slide. Enter the slides with over-sized tenon hole and double holes. And finally a smart fix, the dove-tail slot for the front sight that does away with staking completely.
Having worked with metal, I am well aware of how soft steel really is. When Ruger incorporated the plunger tube with the frame, they eliminated one of the weak points of the 1911 design. I hated that non-traditional feature at first, until I gave it more thought. One less thing that can go wrong as per Murphy's law.