I am confused. What is 10 per week? The multiplier? How did you come by the floor of 2 for 33 year olds?
Training is affected by 3 categories: Age, Trainer level, and Skill distribution, assuming that the player received sufficient playing time at the position being trained and he has not yet received his potential.
In my opinion, it is most efficient to train at 18/19 for newer teams.