I change filters here on the desert mesa every other month....lots of sand and dust. These are the best filters for the job and the price is affordable.
I bought MERV 11. The higher MERV 12 filters are too tight limiting air flow and ultimately causing the AC to over work. This is similar to how the AC FILTER in your motor car works. You may be better off finding a filter similar to a K&N filter which is a super air flow filter but uses oil to filter rather than just paper