If you're in veg you can get rid of just about any pest. The only pest I have ran into that required a take down, sterilization, and new genetics were root aphids and that was because they caused duds.
If the mites are in flower you're fucked. Cut your losses and take the flower room down and clean. In veg hit them with Avid - Forbid - Avid in rotation, 5 days apart. Organic is nice and touchy feely and all, but if you want to get rid of the mites completely, you need pesticides that are made to do the job. You will NEVER eradicate them in flower.
Also, you NEED to figure out how they got in and remove that vector. Otherwise they will just find their way in again.
You shouldn't have to do an ongoing pest control/battle with them. If you have ongoing issues, then you never got rid of them in the first place or you never found out how they are coming in and removed that vector.