Appreciate quick answer(s)!

What would be the best height AFF to centerline of box to rough in a recessed receptacle for a wall-mount flat screen tv?

We need the height for bedroom (watching in bed from slightly higher bed--not one of the super-elevated extremely deep mattresses, nor high footboard beds); den (watching from sofa/loveseat), and great room (mount above fireplace mantle).

Also, is there a "safe" measurement off the centerline of the tv (left or right as viewing the tv) to mount the boxes?

I know measurements of hdtvs are constantly changing, but I'd like to get these installed in approx the right places.

Thanks for your help!

--Mark