Yes, photochromic lenses can wear out over time. The ability of the lenses to change darkness in response to light may diminish after prolonged use. On average, photochromic lenses can last for about two to three years before you may notice a decrease in their effectiveness. However, this lifespan can vary depending on factors such as the brand, quality, and the amount of exposure to sunlight. If you notice that your photochromic lenses are not darkening as effectively as before, it may be a sign that they need to be replaced.