When you give lessons, have at least 2 racquets ready with following specs:
(1) Your favorite poly combo, in your case a poly/multi hybrid. Use this to play points or matches against your student.
(2) A full bed of natural gut, multi, or synthetic gut that you find most comfortable on your arm. Use this for feeding balls. In your 5 hours of lessons, you'd probably be feeding balls for probably 80% of the time. You don't need ultra spin for this purpose, and you will not be hitting hard enough to break the strings really fast. So use the most comfortable setup for this purpose and save your arm.