"Matched set" is nearly a joke. I'm not even sure you can actually GET belts "in matched sets" anymore. Worse, ANY wear or misalignment in the pulleys will cause them to "fight" and accelerate wear between the two.
I used to maintain a big air handler involving a direct fired gas makeup air unit. Had two big "C" belts on it. (Nominally 7/8" wide) I finally pulled one belt off and just ran it as a single. Guess what? Belt life went UP
