Thats what i meant just i used the term 'bored' as a GM used it in a previous discussion. The impression i got was training slows if u do the same training for more then 5 or 6 weeks in a row.
it depends more on the side skills, if the connected skills are higher in comparision to the trained one it goes faster if the trained one is higher is reduced the tempo. If you start like me with player who miss one skill(all my trainee had problems with JS), there is no big problem to train this for a long time.