The best thing you can do for your home is to maintain your windows.  That includes regular cleaning of the inside and outside along with the screens and tracks.  For some that means bi weekly, monthly, or quarterly.  

I have listed several reasons to clean your windows on a regular basis.

• Unfriendly rain water and hard municipal water will build up on your windows and damage the glass, sill and window frames after awhile.  
• Dirt particles get into glass "pores" staining and corroding the windows. You will start to notice will be some light scratches or cracks can lead to needing a full replacement. Cleaning your windows will prevent this the life of your windows will be increased.
• It will increase your curb appeal and home value. 
• In humid or damp climates mold can build up on window glass.