I BOUGHT THIS  AND THE OUTER FILTERS AT THE SAME TIME. BY KEEPING THE OUTER FILTERS CLEAN THIS ONE WILL GO A LONG WAY. I EXPECT IT TO LAST ME 3 TO 5  YEARS. WE WILL SEE HOW THAT GOES. THE FILTER RUNS ABOUT 7 HOURS A DAY AND SOME TIMES AROUND THE CLOCK , I UES THE FILTER TO HELP HEAT THE SHOP. SENCE MOST OF THE HEAT GOES TO THE CELING THE FILTER MOVES 1044 CFM OF AIR THE HEATER DOES NOT.  IT HAS BEEN RUNNING SENCE NOV 29- 13 AND THE FILTER STILL LOOKS LIKE NEW. I WILL UPDATE LATOR IF ANYTHING CHANGES