There can be "sweet spots" - Every room has at least two. But the room should be treated holistically for the most part to get the best results. The most even response throughout the room means a bigger (and arguably much more accurate) "sweet spot" in the long run.
If I understand it correctly... It would be wonderful but practically impossible to optimize the ENTIRE room (especially any vertical, horizontal, and composite corners). On the other hand, "behind the mixing desk", in general seems to be the way most pro studios work (having the engineers and artists in the "zone"... As for me, and most home recordists, the main listening position seems sufficient... Then again, I'm only 21... Someone critique my opinion, please.