A larger front sprocket certainly should wear that sprocket and the chain slightly slower. I read the request for recommendations as a rumor that a larger sprocket shortens engine lifespan not chain lifespan. The engine is certainly working harder with a larger front sprocket. The request wasn't clear on what lifespan shortens and my response wasn't clear on that either. Another thought on chain life and sprocket size. Larger sprockets can also decreases the maximum tension on the chain -- the chain is being pulled by the same shaft torque, but the torque is reduced by the longer "lever" that the shaft has to pull. Works for engine braking too since the maximum amount of braking is controlled by the engine. These probably don't translate into decreased chain wear since we don't usually ride at maximum torque and it just causes riding in a lower gear. If you think I'm wrong, corrections welcome. I DO think the affect is minimal.