I have been using the B+S Pyrocat for about 6 years now (?) and the only time I've had issue with the concentrate was after about 9 months, 1/4 full bottle of solution A went bad.
When tank developing, make sure to mix A + B during the presoak (if you do that) or directly before use, otherwise you'll get a weak image.
And as others have said, the stuff is fairly toxic so use common sense caution. My mother said I developed into a nice young man, but I don't think that was because of drinking the Pcat.