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.
You're right as usual Chris. The reason I don't use two bath now is just because my volume is so low now. If I get to start printing more I'll go back to it. It is better in those ways - but it isn't essential, especially for film. Fix long enough in fresh fixer and this powder will be fine. That time was indeed 5-10 minutes for conventional films, and probably needs to be on the upper end of that range for modern films.
The liquid concentrate Kodafix, which I used to use back in the day, is essentially the same thing sold as a liquid concentrate. More expensive both to buy and to ship, much quicker and easier to mix. Pay your money and make your choice. (Which is some variety of Rapid Fix for me, but these conventional fixers DO work.)