Having personally tested several vitamin C serums over the years, I can attest to the importance of shelf life when choosing a product. Vitamin C, particularly in the L-ascorbic acid form found in CE Ferulic, is notoriously unstable and prone to oxidation, which diminishes its effectiveness and can even irritate sensitive skin. This final shelf life study comparing the OG CE Ferulic formula with approximately seven dupes is a valuable resource for anyone who loves vitamin C skincare. Through my experience, keeping vitamin C serums in dark, cool environments extends their lifespan significantly. When trying dupes, I’ve noticed that some formulas use stabilizers like ferulic acid and vitamin E to enhance longevity, much like the original CE Ferulic. However, packaging also plays a crucial role—air-tight, opaque bottles help protect the product from degrading. If you’re exploring alternatives to the classic CE Ferulic, check for ingredients that support stability and oxidation prevention. Also, be mindful of changes in serum color or smell, as these often signal that the serum has lost potency. Lastly, I encourage you to join conversations and ask questions about vitamin C serums. Shared experiences from cosmetic chemists and skincare enthusiasts alike can guide you in finding the best long-lasting product suited to your skin's needs.