If you go to a smaller rear sprocket, you are raising your gear ratio. The engine will do less rpm in each gear at a given speed than it does now. So, the gears will "last longer". They will all be affected this way. But if you go to too high of a gear ratio, the engine won't have the power to pull the bike, and that gear may be useless. I am reading through this whole thread. Where I am at now someone said the stock rear sprocket is 40 teeth. They had gone to a 33 tooth and were worried they had gone too far, and suggested a 35 tooth might be about right. The front sprocket is just the opposite. To get a higher gear ratio, you would change to a sprocket with more teeth. I used to go buy a one tooth change on the front sprocket would equal about a 3 tooth change on the rear sprocket. The other thing thing you should notice by getting your bike to rev less at a speed, is better gas mileage, unless you find yourself twisting the throttle harder to compensate for the less power you will seem to have. You won't have quite the acceleration you have now, but the bike will seem more relaxed at a certain speed. It's a tradeoff.