He had to complete a 50km race at the international level to get a ticket to Negano. He managed that, under perhaps the toughest conditions possible. On where future improvements in performance will come from. For Gjoko, they will come from skiing more. The weak link in the physical performance chain is not training, but restitution.
Restitution encompasses nutrition, immune function, physical therapy and message, relaxation etc.
The best athletes are able to train more intensely in specific training sessions because they know when to reduce intensity at other times and let the body recover. Even among elite athletes, we see many who are motivated to train hard every day. As a result, every training session is at fairly high intensity. None are sufficiently low enough to promote recovery. And because of chronic fatigue, none are intense enough to drive continued improvement maximal capacity in a body that is already very well trained.