When trying a new product it is wise to not start several products at the same time this is especially true if you have sensitive skin. If a new product is not right for you, you’ll know anywhere from immediately to about three weeks. Hold onto receipts from place of purchase for returns (make sure before you purchase what the return policy is).
But if you are using a product designed to correct problems like age spots it usually takes a minimum of three weeks to see visible changes, to continue to see changes use the whole package until it is gone then decide if the results are worth re purchasing the product. Remember to affect aging skin issues there needs to be a continuance and consistency of specific ingredients to keep the newer glowing skin on the surface. It took a long time to get those wrinkles it will take a while to make them go away. Seek professional help from an Esthetician for recommendations that will meet your needs.