Improper shifting isn't going to increase chain wear. It's just going to increase the chance of chain twisting or failure and put lots of nice little dings in your links. Was your chain mated to a new cogset when installed? If not, that may account for some accelerated wear. Try different lubes (I love DuMonde Tech mtn.) to see which will increase your chain life. Try different chains, too. And and expensive chain won't always last longest - I wore out a Rohloff in four months. Absolutely the last time I buy the most expensive chain!