I know that anecdotal examples don't always hold, but I have some similar
steps in the ground now for ten years, and they appear to have no wear or
deterioration whatsoever. I am 66 years old, and if they last 20 years
for me.............. you know the rest...

BTW, since you mention it, what type of preservative would I ask for at the
big box stores, for me to paint/coat the end cuts ??

Thanks !

James