This was one of the reasons Charlie was hesitant to monkey too much with advanced athletes that had already reached high levels of performance with other training systems. He made marginal changes where he thought necessary, but he pretty much took them as they came to him without trying to reinvent their training. The higher you get on the mountain, the more risky it is to try to jump to another road up. There is a large degree of path dependence. Derek can probably provide more insight on this point since he witnessed a lot of it first hand.