Does anyone know how long the Arista Premium will keep in both an unopened and opened half used bottle? I use 5L jugs of Ilford Hypam rapid fixer which have to be shipped for significant sums but I just priced the Arista liquid concentrate 64oz size from Freestyle and found that it would be much cheaper to ship even in quantity. Presently using the Ilford Hypam, I fix fiber prints for 1 minute and film for 2 minutes using fresh fixer. Would my times be the same with the Arista? I assume it is ammonium thio as well.