Let me clarify: 2 bath fixing is cheap insurance and better economy of fixer. As the 1st bath begins to approach capacity it's not removing all complexes. A 2nd bath ensures these are removed while at the same time allowing the 1st fixer to safety be used to capacity.
. When my volume is low I usually use whatever fixer baths are around or 1-shot concentrate mixes but yeah I use 2-bath when printing or large runs of film.