Shifters, brakes, cranks, hubs and even wheels can last a ridiculously long time. For years, I hated my road bike and wanted a new one. Would the components die? No! It sucked! 10 years of abuse, crashing and little to no maintenance, and they worked great. All I ever did was change brake pads, cables and chains. I could never say, "Oh hey, my bike is trashed, I should get a new one". Then I said to myself, "Hey, you've got a job - just go buy a new bike". So I did. My old bike has thousands of commuting/crashing/racing miles on it, and is still running strong. I've converted one wheel to SS, and I'm cannibalizing another to make a fixie rear with an old FW hub I have, but everything else is intact.
CN: having an extra year on some of your components will not make much of a difference to their overall lifespan.