I've noticed that anti-foam can seperate after a few years, but if it is still sealed it should be ok. One other thing I learned from my supplier (I sell BioGuard and SpaGuard brand chems) is that if any of the liquids freeze, they can seperate or lose their effectiveness.
Any chems that are solid should hold their value.
Test strips, however, do expire and they should have an expiration date on the bottle somewhere. But, as ndabunka said, if you aren't sure, toss them.