Quote Originally Posted by john_s View Post
Even if some of the ingredients are not fully dispersed amongst the different batches it can hardly make a difference. I wouldn't hesitate to mix up small batches of powdered fixer.

It's not like developer where, for example, tiny amounts of phenidone or bromide could be unequally dispersed, making different batches behave differently.
I guess as long as you have a good return policy on the prints you're selling/giving away, then it's okay to use fixer that may or may not do the job from batch to batch.