What type of chain are you buying. I have gotten about 3k on chains for the last 10 years. I ride in all kinds of weather and change them around the 75% mark. I do not get the nickel plated chains (reduce rust) as I find it less expensive to buy a non nickel sram 10 speed and change them around 3k. I clean them every few months but do use very good lube every few weeks called gold link. It really does a good job keeping the chain clean. I ride really hard but usually do not change cassettes until about every 8 chains which is the recommended rotation.

I blow through chains on my mountain bike way earlier but that is really hard core riding. It's still about once per year but way less miles.