OP, congrats! I do not want to sound negative, but don't you want to know if your output is affected by the developer age? I am not an expert in film development, but simply reading manufacturer's data sheets I've concluded that the output quality degrades gradually, depending on developer's age, storing conditions, dilution and replenishment rate. It's not a binary on-off switch.
I am not brave enough to follow your footsteps. I just dumped half a liter of unused ID-11 because it sat under the sink longer than Ilford's storage time recommendation. I am sure it works, but I do not know how much quality I'd lose if I used it.