The effectiveness of most cleaning products can be decreased over time, despite their long shelf lives. Pods can last up to 18 months, which makes them a safe bulk purchase. Generally, you should replace dishwasher detergent bottles every three months for other types. A dishwasher detergent comprises enzymes and chemicals that assist in softening water, removing grease and grime, and preventing bacterial growth. If you use expired dishwasher detergent, many of these properties will no longer be as effective in cleaning and sanitizing your dishes.