That depends on the manufacturer. High quality filters such as Can filters or PHAT filters will last from 2- 3 years of continuous use. They can be repacked but its really not worth it by the time you by the carbon and get it in the odds of it working as well as when you got it are slim and none, These filters are professionally manufactured for long lasting unsurpassed duality while the average Joe at home cant possibly pack the carbon properly. After 3 years of use you should feel no worries about replacing it. I’m sure it has given you your moneys worth from it long ago.