That actually depends on the ingredients in the sauce. Most barbecue, sweet and sour, and similar sauces are comprised of a varying mixture of salt, vinegar, sugar, and water with occasionally vegetables, like salsa, or alcohol. All in all, those are mostly preservatives. Also, I specifically say reheat, not recook. You simply bring the pot of water to a steam, or right as it boils, and cut the heat. Then I add the jar of sauce to warm up and use a knife, stirring rods, stainless steel straws if you're in california, to stir it as cooling in the fridge can congeal some sauces between uses. I've found sauce recipes that might be quoted as lasting three weeks with refrigeration, lasts several times longer with this method. I've experienced no problems doing this with one exception, dairy and meat based sauces. Those I will freeze to preserve them, but I thaw them out before putting them into glass cookware then employ my reheating method. So, it goes without being said, I've got a good variety of oven/stove safe cookware in my kitchen.