That is what I thought, too, but I'm pretty sure that he is already on his fifth (if not even sixth) week of training and yet there is still no change. And out of those 5-6 weeks, he got at least 3 weeks of training last season when he was 26 years old. I thought that would count for something.
But to answer your question, I wasn't really planning to train him this long, but with every new week that he wouldn't pop, I thought "OK, I'll train him one more week and that is it". I'm pretty sure we all had that kind of moment at least once while playing this game.
Anyway, what do you estimate? Should I try "one more week" or should I just give up?