Yeah I agree that FT and ST are important skills. But they actually NEVER decrease in efficiency. A 40yo will train FT just as fast as an 18yo will. In addition Team Training is not affected by Trainer level.
I still stick to my original number that you lose an entire seasons worth of total pops when all is said and done. But one may argue that those team skills are worth it, and they very well may be. I think Stamina is the most undertrained skill in he game behind maybe JR