I think this is a great point. The thought occured to me today that an instructor probably takes on a different meaning or role as one progresses.
I'm certainly not at that point, but I'm thinking of the various schools that we read about in music history. The Mighty 5, Les Six, etc. These and other relationships through history were undoubtedly people who could keep each other focused and on track so to speak.
I think time with and without an instructor is valuable. As I noted earlier I'm without an instructor and am somewhat at a standstill creatively; I feel like I've lost my way in a manner of speaking. That's what motivates me to search out someone who can be instructively critical.
Steve Winkler