Bustle.com just came out with the article “How Often Should You Wash Your Jeans?“. I think that is a great question. I am in favor of washing clothing only when it really needs to be washed, but when is that?
Bustle and Business Insider say that you should test the cleanliness of your jeans by their smell. Smelly jeans= dirty jeans. I think that this is a great way to tell when to throw your pair in the wash.
Take a look at my page on Washing Machines to further optimize your jean-cleaning!