I started using this product (along with the daily moisturizer with SPF) a little over three years ago. I moved from a humid climate and found the dry climate (while preferable) had taken a hard toll on my skin, particularly my face. I started using the serum and moisturizer every night, and I could tell a huge difference in my face after about 3 months. Since then, these two products are part of my daily skin care and I continue to order them even when I am living out of state.