Like Tom said, if it isn't giving you issues, don't waste the time sending it in. Are your photos coming out nice and sharp, is the AF working properly, any of the focus/zoom rings sticking? No reason to send it in, IMO. You can relax, this gear is pretty robust, you don't have to worry
Now, like Pigpen101 mentioned, if you're someone who's hard on gear and it's used as a tool (i.e. not mollycoddled like us hobbyists do), regular maintenance on the tools is warranted. Or, if you are unfortunate and have had any hard drops, scratched glass, salt watered, fungus growth, stuff like that, I'd definitely send it in to get fixed.
Last weekend at an event, I saw a photog using one of the dual Black Rapid straps w/ a 1DxII + 24-70 on one, and a 1DxII + 70-200 on the other... guy is shooting, gets his shots, and then basically lets go/drops the rig, and it swings around and collides with the other rig behind his back. It was a sickening sound to hear But hey, his focus was on getting shots, not babying a tool; he probably wouldn't send the gear in unless it flat out stopped working at a gig.