Knock on wood, I never had a mite problem and have some cultures still producing 6+ months out.
My biggest culprit are phorid fly invasions and drying out during summer months, as I keep my cultures in my shed.
Granted I separate my older cultures from the new ones but as long as they yield a few dozen flies a week I keep them around. Plus as they get older they produce smaller flies perfect for froglets. I wonder if mites are more prevalent in the home vs. other areas.