Spade said:
thats a diff one for me to answer.... .

I would say, it depends on many factors: some examples are
are you training the same position in jrs? If yes and also if i am not training the same position in srs then i would keep him in jr till red p.

Do you need that player in your sr team? will it affect your winning chances if he is on board? if yes then promote him.

Are you planning to sell him? will he train better or gain more experience in your sr team?

there are many better pundits who will answer this question in better detail. these are my two cents.