WeThreeKings
Demidov is a HAB
Won’t make a huge difference in the long run. Athletic success is determined mostly by talent and natural ability, which will not disappear in seven months.
There are certain stages where development happens at quicker intervals - not actually playing hockey and getting repetitions in game situations is still a negative drain on that fertile period.
It's not going to break him because he's special but it's not ideal either and can either delay him reaching his potential or shave off part of his ceiling.