I have the cheap park tool chain checker also. It works very well. If you change the chains before they were much, you will really cut down on the wear of your rear cluster and chain rings. Running a worn chain too long will wear the rear cluster. When you finally change the chain, the chain will skip on the worn rear cluster. The rear cluster will have to be changed and that costs about 2-3 times what the chain costs.

I believe that cleaning your chain frequently will reduce its rate of wear. I get about 3,000-4,000 miles on a chain.