In an airtight container, place sugar and vanilla beans. (Break or cut beans as needed to fit into your chosen container.) Seal, and store in a cool, dry place, shaking every few days. Sugar will be scented and ready to use within 2 to 3 weeks; it will become stronger in flavor the longer it sits. If desired, pulse the mixture in a coffee or spice grinder just until vanilla beans are finely ground. Store in a cool, dry place for up to 2 years.