Once your eyelashes reach their maximum length, they enter the resting phase. Your eyelashes spend far more time in the resting phase than your scalp hair does. When a hair from your head falls out, it is quickly replaced with a new hair. When an old eyelash falls out, it takes a much longer time for a new one to replace it. In fact, if an eyelash gets pulled out, it can take up to two months for a new one to grow in its place. This is why it seems like your eyelashes do not grow. They are growing--just very slowly.