Choose the correct predator insects and yes they do get rid of spider mites, completely and absolutely
The best ones to eradicate spider mites are called
Phytoseiulus Persimilis
and you can buy them from amazon
I've used them successfully, more than once, years ago when I got clones that came with spider mites from a friend who didn't keep a clean grow
i've never known anyone who eradicated them entirely with predator mites alone. every single one of them had to shut the grow for it to happen, and then use a chemical clean.
as long as they ran perpetual they needed to constantly monitor and would add more predator mites on a semi-regular basis. it allowed them to grow without chemicals and get to finish, but there was a population of both the entire way.
predator mites are one of the few things safe to use in flower. you will need to bud wash at finish though.