Last year, I insulated my attic air handler. Actually, I did it on the top surfaces, and even left some uncovered when I ran out of poly-iso
I recently finished the unfinished part, and then remembered I had not insulated the bottom on the ductwork.
So I recently covered the 15 feet that carried the most air. I have more poly iso to put in place on the other end of the ductowrk, but am chipping away at it.