Well so far the past 3 weeks I've managed to get at least 5 on 48+ minutes and 2 of the weeks I got all 6 so haven't had to much trouble so far. But I ranked my players in order of best trainee. So I'm training my 2 best trainees to get 48+ minutes first, then if they do that in the first game then I train 3rd and 4th trainee in next game etc. I've had 11 popups in 3 weeks though so been happy with that :)