Very interesting mantel supports you have there...never seen it done that way. Did you do it so you don't have to deface the front facing masonry? Very nice stone work.
Also the Buck 91 has a GIGANTIC firebox. Isn't it like 4 cu ft? You must be able to push 24 hours with that if you wanted depending your BTU load.
House was built in 76, builder was the first owner, we are the 3rd. He crafted the supports. They are pinned into the stone. I believe the size of the 91 firebox is about that. Our usual burn times are typically 12-14 hours of usable heat. Mostly burning red/white oak and hickory. It often takes 24-36 hours for the fan to cycle off if not reloaded. Our home is 1800 sqft, with a full basement, the Buck does most of the heat work.