All depending on they type of seeds they can be easily saved.
Most seeds can be dried out in a paper bag or on top of newspaper on a cool, dry and dark shelf. After about 1-3 weeks of drying they can be stored in a similar fashion either in paper envelopes or jars with silica gel inserts. The key is to keep them cool and dry.
When kept under good conditions collected seed can last up to 5 years and when kept under perfect conditions up to 10 years!