Well I have a different perspective on this, since I train once a week with a Kru and twice a week at my university with a group of students from all sorts of martial arts, mostly kickboxing and muay thai, but also some students of tae kwon do. We run a very loose society, where we encourage free sparring, exchanging techniques and tips, and although no one is in charge or conducting the class, we get a lot done and we all feel as if we've learned a lot from the experience.
Of course, quite a few of us have more than 5 years of MA experience under our belts, so we are also aware of maintaining proper safety, which I think is the crucial thing for any martial arts instruction. So I guess the amount of years training isn't as important as your style of training, and the only thing that is absolutely essential is proper safety training.