Freeze 12 is junk. You're better off to switch back to R12.
The repair company I work for, at one store the manager had a woodie for Freeze 12 for a short while, not much before I went to work there. It got to the point where when a car would come in for a/c repairs, if we'd done a Freeze 12 conversion the year before, we credited that repair cost towards the repairs they were now needing.
I wouldn't convert to R134a, either. R12 is the best, pay the extra money for the more expensive refirgerant.
Of course, it's insanely hot here, so a/c performance is much more important than cost savings.