The safe answer to this question, like with most other food items, is 3-5 days. Since we have not had the recipe tested, that would be our official recommendation. However, common sense suggests a much longer shelf life when kept refrigerated. In fact, virtually every ingredient in mustard BBQ sauce is an item that does not even require refrigeration. And many of those are used in other applications as preservatives (vinegar, salt, sugar, etc.) Simply understand the risks if you choose to use your homemade mustard BBQ sauce after the safe period we recommend. According to the nutrition label on Maurice's Southern Gold mustard sauce, if you refrigerate after opening, the sauce is "best used within six months."