I see from the photo. formulary website there are several "flavors" of Pyrocat. Pyrocat HD, Pyrocat MC, and both with glycol. It appears that MC is the more energetic of the two, but I didn't see anywhere in the literature what the glycol does - in other words, what's the difference between HD with, and without the glycol?
As Jim said. I typically process big batches of film only a few times a year. Pyrocat HD has a 6-month shelf life once opened, Pyrocat HD in Glycol lasts indefinitely. I buy the glycol version so that I'm sure my developer is going to be good when I go to use it.