I'm sure the Ilford Ilfotol will also be very long lived. It is just a concentrated surfactant, so oxidation isn't an issue.

Just for clarity, you only mix up what you need each time, leaving the rest of the concentrate in its original container.

Using Ilford's data sheets, 100ml of stock ID-11 has the capacity to develop one film, so if you dilute ID-11 stock 1 + 2 one litre of stock will develop 10 rolls.

The Kodak regular (non-hardening) fixer is available in powder - Ilford doesn't make a powder fixer. The Kodak fixer will fix 26 films for each litre of working strength solution.