Built-in gas grills can feasibly last up to 15-years if they are properly taken care of and maintained. Spending more initially may help, but doesn't guarantee, a long-lasting appliance, and you should ensure that you are cleaning your grill appropriately and checking for imperfections such as rusting on a regular basis. You will likely need to replace elements of your grill, like the cooking grates, before you need to buy a whole new one.