Given the size of my room (small), I haven't had to worry about my frequency response in multiple locations. I have a love seat in my room and the graphs don't change much in the two or three possible seating locations.
My room is primarily used for audio...thus, the small room works for me. When I listen to music, it is always a solo affair. Thus, I optimized my system for the sweet spot only. Yes, we do watch movies in there also, just not nearly as much listening to music (probably 80% music, 20% movies).
As you've pointed out, I suspect EQing a large room is a whole different ball game.
David