When taken care of the right way, MEC pots can last a very long time. But there are some who like to replace their unglazed, pure-clay pots once a year or at least once every 2 years. That’s because it’s believed that in this time, when used everyday or almost everyday, the food has “taken” all the nutrients from the clay, whenever needed. And also because the pot has “shrunk” to a point where it can no longer fortify food with oxygen. Being porous, the pot allows food to “take in” oxygen while cooking, but it slowly shrinks over time and many uses and the pores come closer together preventing this feature.
Those aware about the nutritional fortification and the pots ability to “breath” change theirs every 1-2 years. However the pot itself is functional and cooks your food even after this time period.