For teachers who stay with you for the long term, you may consider graduating them from mentees to “full” teachers. You should be able to increase their pay and reduce the amount of training time they spend with you at this stage.
I recommend considering moving in this direction on a phased basis for any teacher who has been with you for a minimum of 2 years. Everyone is different; so if you feel they still need weekly training sessions and a lot of oversight in their 3rd, 4th and 5th years with you, that’s fine. Keep up the full mentee support system until you both feel ready for them to have more independence and responsibility.