Mike Barry (Canada's "Mr. Bicycle" and father of TdF racer Michael Barry) says steel chainrings wore faster in his experience racing in the 1950s-60s than aluminum ones. He doesn't know why this should be but says on his blog that he suspects the aluminum makes an early accommodation to the precise shaping of the chain rollers and then stops wearing. Steel always puts up a fight and therefore keeps wearing away. Voice of experience, fwiw.

Replacing worn chains is certainly important. If the pitch of the chain elongates it's going to present an ever-changing wearing force against the teeth of the rings.