I'm not a lawyer, but my understanding has always been that the copyright notice isn't required at all. If you get into a dispute over the ownership of something, you just need a way to prove you're the actual copyright owner. I don't see how a small line of text on the page will help you do that (especially since you can arbitrarily change it whenever you want).

I keep mine up to date on my sites just because it's basically a staple of modern web design. Not having it would be weird, and having it out of date would probably confuse people.