I own an Airstream and have polished it to a very shiny finish. The problem is the mirror finish disappears after about 3 months, due to oxidation and I have to buff it all over again. There is no way to stop the oxidation unless you paint it.
To get a mirror finish like that on a 22' trailer, I estimate that it took at least 400 to 500 hours with a good polisher like a Makita, and 3 different polishing compounds and
a lot of wool bonnets and rags. The more you polish it however, the easier it gets to restore the luster.
Dick