Microfilm doesn't use cellulose acetate, and is stable for centuries with minor storage requirements (room temperature, low humidity)-- the same that are required by books.
How widely it was used prior to that time, and what filmstock selection practices specific institutions followed I don't know, though I suspect these may have varied.
As for current polyester filmstock:
Black-and-white polyester film has a life expectancy of 500+ years under proper storage conditions.