Found this letter from Fox Farm...

Hello,
Our liquid nutrients do go bad except the Big Bloom. Tiger Bloom and Grow Big have a life of 2 to 3 years but Big Bloom gets better with age. After 2 to 3 years the microbial activity starts to die, the product probably still has some nutrients left, but not all that it had. Let us know if thereā??s any other questions, have a nice day.

Customer Service
FoxFarm Soil & Fertilizer Co.
P.O. Box 787
Arcata,CA 95518
(707)-443-4369
(707)-443-7645

I would say that it could last 2 years if stored in perfect dark conditions.
I know that Botanicare says to ditch after 1 year. If they look bad or are clumpy I would buy new ones