In our 1200 sf house, space is at a premium. I mounted a 46" TV over the fireplace mantle. Top of the mantle was 60". I cut in recept, coax and HDMI. Top of the tile surround of the fireplace is at 40". Bottom of the TV was at 64" AFF. I started watching TV standing up to avoid neck-ache.
I removed the mantle and lowered the TV over a foot to 50" AFF. The wife was concerned about melting the TV. As a compromise, I installed a 4" deep shelf at 47" AFF with cup hooks for Christmas stockings. I was still watching TV standing up.
I convinced the wife to put the TV back on its factory stand and place it on a "buffet" table next to the fireplace (bottom of TV at 37"). I placed a huge mirror over all the holes over the fireplace.
The couch is 11 feet away, and that is where I SIT to watch TV!