If you've only been training it for 4 weeks, it seems rather hasty to assume JS and JR train in 5 weeks, as you can't possibly have had 2 pops on them to gauge the time between pops.
first of all it is hasty, but I wont train 1on1 next week, so I rather decided to share my observations now.
In those 4 weeks I have had 20 times players getting 100% training.
(5 trainees got 100% all 4 weeks)
I have had 4 pops in IS and 4 pops in JS
20/4 = 5 weeks
so it might be 4..4 to get a pop or it might take 5.5 weeks to get a pop.
this calculation is not perfect but a lot better then having no results. Unless someone is going to train 1on1 on forwards for more than 5 weeks it is the best we have.