This answer depends on lots of variables. For instance, if you intend to keep the pellet grill outside but not covered compared to the best-case scenario of storing the pellet grill in your garage when not in use.

With any painted carbon steel pellet grill/smoker, at some point, corrosion is going to damage the paint finish. How long that actually takes will depend on how good the paint finish actually is.

The best pellet grills to resist corrosion are obviously stainless steel pellet grills which you can search for through our database.

With pellet grills/smokers, they obviously have a lot of electrical components, with some of them being consumable parts (at some point, the hot rod igniter will definitely need replacing). 

A well maintained pellet grill/smoker should easily have a life span of 5 to 10 years, potentially longer in the case of the stainless steel pellet grills.