I think the “fade” happens when they are left bare over a period of a few years through severe winters. You cannot “fix” it after it happens, just cover in the worst seasons and enjoy it until you pass it along to the next owner.
It’s a little bit like a Patek Phillipe watch…
“We do not “own” these, we are merely caretakers for the next generation.”
Get it standing tall and instill a little respect for a child or grand child and it will last another generation!