serums in general are usually moisturizing anyways, and most would be considered moisturizers to some degree...so if your skin feels soft, and you like the results, then continue to use what works for you! the point of moisturizer is to create a barrier for your skin to keep in moisture. your skin produces it's own oils, but sometimes you need a little help. i would say if you are 25 or older, you should be putting something on your face at night. i use a chemical exfoliant (retin-a) followed by a medium weight moisturizer with antioxidants.