If you still have the lipstick you bought three years ago, chuck it! Unless you're keeping it for an upcoming science fair or sentimental reason, the lipstick has got to go. Unlike food, makeup and skincare products don't have an expiration date. That doesn't mean your concealer can last you until you're well into your forties; the FDA just doesn't have any guidelines for makeup care.     First, organize your makeup bag. Anything that is dried-out or smells funny should be thrown out. Sometimes…