A year and a half ago I bought a box of Paterson FX-50 film developer (the environment friendly one - remember). Two days back I decided to try it on a few rolls of T-max 100 from a nigh shoot. The negatives came out very thin but still with some detail distinguishible. When I developed another roll using my regular developer (HC-110) it turned out to have much more detail. The question is: Is it common that developers in unopened boxes "go bad" like this one obviously has? Are certain types more likely than others (what about Xtol?) to perish.