For me, this is an opinion I have acquired over many years of tossing the TV topic back and forth with dozens, nay — hundreds! — of people, including other designers, clients, spouses, kids, and contractors, and I always land on the side of don’t.
If you already have your TV hanging over the mantle, could I persuade you to consider moving it to a less prominent place?
For the sake of your cervical spine and proper alignment when gazing at anything for very long, your TV should be — whether freestanding or hung — positioned at eye level when you are sitting down. (The ergonomics issue also applies to your cell phone, we are all going to end up with hump-necks if we keep gazing down at our devices.) In a living room, the sightline from your seating area is often much lower than the space above your mantle.
(And if you dig through my portfolio archives, yes, you will find a few homes where the TV ended up above the fireplace. Or is your primary intention to create a warm, welcoming space, filled with fun art, vibrant energy, and a tone of elegance. If you want to increase the energy, joy, and pleasure that you can have in your life through the interior design choices you make, don’t make the TV the focal point of your living room or family room.