the longer a guy has the same coach, knows the system, lives in the same town, etc. he is going to be more comfortable. Also, the coaching staff will get to know where and how much he needs to train in order to improvethis is not possible with our system - level of our coach falls down by the time and BBs want you to replace staff once upon a time - so it shouldn't depend of a time spent by your trainer in your team
but could be a nice option to maintain a lvl 7 coach paying him the lvl 10 salary until a new coach lvl 10 will be elegible...