How high to mount my TV monitor?

Proper TV hight should be near eye level. When I design home theater cabinets or Home theater screens I usually start at 36" off the floor for bottom edge of screen. I'll make adjustments up or down a few inches from there if needed. The screen over the fireplace can work, but I am not a big fan. Yes, you will be looking up. No, it's not optimal. Now you can't put anything on the mantle or it's in the way. You can raise the screen higher. It's even worse for viewing now.

All the screens are high at your local sports bar. It's not bad for eating with friends and watching the big plays. Go out for dinner sometime and see how you like it.

Over the fireplace works well in a master suite with one of those high beds. High screen placment works well in a game or rec room where people might be mixed seated and standing playing pool or at bar stools. The center channel should be right under the lower edge of the screen. If you do this in a rec room the center speaker won't get blocked by furniture to those located in the back of the room.

For a living room or family room I would look for lower placment elsewhere.

It is 6 feet to the center of the screen. When I sit back in my couch I am looking directly at the center of the T.V..
Not many people sit with their back vertical to the floor so this makes sense to me.The 13 feet is from your eyes when lying back on the couch.

I think that putting a TV above the fireplace is one of the great examples of "interior decorators" putting form over function. Maybe it looks pretty for photo shoots for magazines, but I have never been in a room with such a set-up where I didn't have to look up, and within a very short period of time, I start to feel the strain in my neck.

However, what I think doesn't matter a rat's butt, or so people tell me from time to time. So all I can say, give it a try, and if your neck still feels fine after watching the Star Wars or Lord of the Rings trilogy, then go for it.

Of course, a Lay-Z-Boy recliner would solve potential problems too. Get one with a cup holder for beer, ...and a pocket for your remote(s).

Actually, the proper height should be when you are looking at the screen your eyes are level with the bottom 3rd of the screen. Unfortunately this is not practical in most theater setups.