Steve Voigt
It's in the literature.

Where?

If you actually use a plane to dress wood you will [w]ear it out…

I do use plane to "dress" (i.e. dimension) wood, every single day. I don't retail tools for a living; I make them for a living.

…and what was done is the newest planes were used for final jointing and smoothing, as they wore they were demoted to lesser tasks.

I would love to see a period reference for this claim; I have never seen it except for 20th century writers, mostly bloggers and forum keyboard warriors. On its face, it doesn't make much sense: plane tasks are specific to size. I can't imagine roughing out parts with a worn out smoother--I would use a jack plane.

On the other hand, I have seen multiple period references that suggest using a single iron jack to scrub off the rough surface, dirt, and grit before dimensioning with double iron planes. I can provide quotes and citations if anyone is interested.

BTW if you are wondering why it is pretty easy to find late 18th century molding and special planes but late 18th century wooden smooth planes are very rare - it's because the most used planes wore out.

You are talking 250 years ago. Yes, smoothing planes will eventually wear out over several lifetimes. I might even wear mine out in one. A try plane will wear out faster, and a jack will wear out faster still.I was specifically rebutting your claim that smoothing plane would require frequent replacement, which is simply not true.