I have yet to have anyone complain about too large of a TV and I constantly talk up to a larger size. Half the time I'm not even selling them the TV, I'm just hanging it.
We sit about 12' from an 85" TV, and if we could get a reasonably priced 98" TV, I would've used that instead. There is no fatigue, and a 1.5x viewing distance to the WIDTH is considered common. In reality, 10" to 12" of diagonal is comfortable for most viewers for each foot of viewing distance. So, yes, from 8' viewing distance (eyes to screen), having a 75" to 85" diagonal would actually be quite comfortable for most viewers. 65" is no problem at all. Be very aware of your eyes to screen distance, not the couch to screen distance. Also, try moving the couch a couple of feet closer for a day or two. See how you like the screen size. Sitting about 6' viewing distance for a 55" would be similar to sitting 8' away from a 75" screen.