I have been Triple-Thicking my back glasses for the past 20 years. It is just perfect and does not budge.
You have to apply a very light coat first , let it dry ...... and go with heavier coat later on.
I have had these backglasses outside in a shed, in North Carolina where temperature varies from 105 down to low 30's, with no issues. That was for about two years. It is always better to keep them in controlled temperature and humidity.