From my experience, the need to reapply sunscreen every two hours really hinges on what kind of day you have ahead and how much UV exposure you encounter. For instance, if you're spending time outdoors during peak sunlight—activities like hiking, swimming, or paddleboarding—reapplying sunscreen liberally every two hours (or even more often if you're sweating or in water) is crucial to protect your skin from damage and reduce the risk of sunburn. However, for indoor days filled with mostly desk work or errands, the situation is different. UV damage is indeed cumulative and doesn't require visible sunburn to cause long-term harm like photoaging and hyperpigmentation. I personally apply a generous amount of broad-spectrum sunscreen in the morning, about a 'fat two fingers worth,' focusing on products known for high protection. If I stay indoors most of the day, I don’t obsess over reapplying every two hours—just ensuring I reapply before stepping outside. The California sun, for example, can be intense even after spending hours indoors. It’s also important to consider your skin goals and current treatments. If you’re using active ingredients like retinoids or acids, recovering from procedures, or addressing hyperpigmentation, consistent sunscreen use becomes even more critical. In these cases, I recommend sticking closely to reapplication guidelines. Finding a sunscreen with a durable, water-resistant film is a game-changer for longer outdoor sessions. Brands like Biore Athlizm and Anessa offer options that hold up well against sweat and water, giving you peace of mind without constant reapplication. Ultimately, sunscreen isn’t a one-size-fits-all solution. Adapt your sunscreen routine to your daily UV exposure, skin needs, and personal tolerance to risk. Remember, in high exposure settings, more sunscreen and more frequent application are always better to help prevent serious skin issues like squamous cell carcinoma. But on low exposure days, focus on protecting your skin with a solid morning application and reapply whenever you go outside—this balanced approach has helped me maintain healthy skin without the stress of constant reapplication.