It completely depends on your utility, the more you use it the sooner you will require it . (Eg. For a product like saucepan that you use daily to make tea, kalai might be required in 3-4 months) but using wooden spatulas for products like karahi should help. Make sure your cleaning material is not abrasive. Just a simple takeaway would be you don't have to scratch the tin coating in any way. Do not leave it on gas without oil as Kalai might melt leading to quick fading of the coating.