Most of your more affordable vendors require steeping. They are usually made to order, and need a little time to blend, deepen, soften, etc. Like mentioned before, the heavier flavors, like creams or desserts or even tobaccos require more time. While lighter flavors like fruits and some candies, not so much. They may be in need of breathing, however. If it smells perfumey, or like alcohol FOOB, leave the cap off for a few hours, letting the fumes escape.