How often do you wash your sheets?

So after getting allergy tested and finding out that trees aren't my friends and that my bed could be making me sneeze because of dust mites. I have been working on making my room more allergy friendly, and its going to take a while. Some of the first steps have been to order pillow, mattress, and duvet covers that block the dust mights. I'm also starting to changing my sheets more regularly. I'm totally guilty of leaving them on to long, but that said I usually shower at night so I'm not dirty with the days grim getting in my bed. Now my goal is to change them once a week, which means more washing :(. How often do most people change their sheets? What other things have people done to help with dust mite and tree allergies? Thankfully my doctor doesn't seem to crazy about getting rid of anything just making small changes to my routines.  So I leave you with a trick for storing sheets, pretty sheets and pretty more allergy friendly bedrooms. All images linked to my pinterest account http://pinterest.com/aliinar/my-one-day-city-cottage/

Matching Sheets Fold up and put inside pillowcase