Graham is correct!

Bleach will keep for a year or more unused, even in partly filled bottles. Fix will keep until it begins to get cloudy, or about 6 months or longer.

Stabilzer keeps unused forever or until bugs start to grow in it. You see that as thready filaments. I have never gotten bugs though others report that they have. Bugs don't like formalin so I believe that it is not a common event to even have stabilzer go bad at all.

My developer is still good after 6 months in closed nitrogen blanketed containers. It is bad when it begins to turn from straw colored to coffee colored. A dip test with leader will help you check it out. It should develop a piece of leader to dmax in about 20 mins at 70 deg F or 20 deg C.