If you feel comfortable with the spray your using and that it will not effect the smoke, keep using it. Especially since it seems to be helping. If you are not having problems at that point; I would discontinue spraying anything the last week. If you still have some mite activity when you are drying simply cut your branches short and hang them upside down. The mites naturally climb up and you can vacuum them off the hanging string. You will not get them all and it is far from ideal but it will get a lot off.