I have heard of the McGuire Program and have actually spoken to a few people from there who use the technique. Seems effective from what I heard but I nothing any technique will be exhausting after awhile. I did a fluency shaping course called HCRI a while back and they promised the same thing: that my new speech would become habitual and natural. After coming home from that program, I really put the work in to maintain my speech but it didn't matter because my old habits eventually returned. It only served as a temporary fix, a band-aid.