I am, by nature, an auto-didact and find that one lesson every decade seems to keep me going
Seriously, though, I think, for some of us, all we need is the occasional lesson to keep us on course and then the rest of the time is spent with self-teaching. I have never really been able to afford regular lessons so have just figured it all out myself. There are gaps but, like 90% of us, I have more technique that I can really use and most of the shortcomings in my playing are about a lack of REHEARSAL rather than a lack of knowledge.
Where basis theory is concerned, there is not THAT much to learn but it does take a long time to internalise things and to incorporate the concepts into one's playing. It is a case of whatever works for you.