The filter required to help keep your air dry will very greatly with the environment the compressor is used in. The filter/water separator, up top of this thread,is great for medium or higher humidity areas. While a cotton filter alone may be good for a low humidity area. One of the other filters shown low in the post from
Long_Gun_Dallas would werq well for medium to low humidity areas.
My basement has 55-65% humidity and I run one of the small Yong Heng Type filter cotton filters just before my three media gold filter. I purge the system every five minutes, while in use, and change out the Yong Heng filter every twenty and my three media filter lasts about a year. I have a second Yong Heng cotton filter that is run after the media filter. When it gets damp I know it is time to change out my media filter.
This system has werqed very well for a year now and I checked my tanks for water intrusion on two occasions and found no sign of it.
If you purchase a media filter and have to change it very often you need to upgrade your filter arrangement.