That's why I put the powders in glass bottles and left some space in there. I can just invert it a couple of times and all the components will mix.
I don't need a gallon of fixer standing around somewhere and more importantly, I can't risk inconsistencies. I put a LOT of time and effort to expose the film properly, so I don't want to think that my 6 month old fixer might need a 5% increase in development.
BUT, I know which powder is which!
I need to know just the masses I had.