Hey Nelson, I've only just found this thread so I hope my advice is good if you need it but I hope you don't!
I had a bad infection in my greenhouse and the EU have been cutting hard back on chemicals that amateurs can use, so there is almost nothing on the market (here) that is effective that is chemical based because it's all been around for years and like most pests that have a quick life/breeding cycle resistance builds up very quickly to whatever you use, especially if you only use one type of insecticide, I'm afraid to say that you will probably get re-occurence of resistant mites sooner or later.
The pest thing that you can use are biological pest controls, they work and they work well, the down side is that you have to have some level of infestation first because they need something to feed on so that they can breed and they won't multiply below certain temperatures (not that that would be a problem in a growroom) some times repeat applications are needed but again that is usually down to temperature drop or because they are so successful they run out of prey and die out!
I have used them and heartily recommend them (I'm presuming they're available in your neck of the woods) and can be delivered to your door through internet mail order, they are more expensive than chemicals but there is obviously no concerns with toxic chemicals on your herb and considering the value of your grow the price pales in to insignificance.
Hope this helps.
Jim