It was just before mid-season last season. I don't believe there was a definitie time period.
There was an overall speedup, with a specific tilting toward younger players.
My recollection may be faulty, but I think in the discussion after the announcement it was implied that the training rates could be gradually lessened. They may be wanting to strike a balance between an initial lack of skills, and ending up with HT where there were bunches of overtrained players.