Some reagents will go bad in a shorter time than others. If you keep your test kit in the house and not in the garage or shedthen the only reagents that are likely to need replacement after a season are the DPD liquids or the FAS-DPD titrants (assuming you have a Taylor K-2005 or K-2006) I have also seen phenol red pH reagent go bad but it usually lasts a few years before it does. Reagents for acid and base demand, TA, CH and CYA and OTO tend to have long shelf lives. DPD powder for the FAS-DPD test is usually good unless it has formed a solid lump in the jar or has turned completely black.