As is the case with any other product, kettles have exposures that do not let them last forever. There are several signs that tell you that it is time to buy a new one. One thing that makes you change your kettle very often, is rust. It accumulates, weakening the metal, making it exposed to structural defects. This, also, endangers the quality of water. Another sign, is the crooked spout suffering deformation, after an impact. In this case, you have to buy immediately another kettle, as the old one can fail pouring the water in a straight stream.
An important factor influencing the functionality of a kettle, is the minerals residing the interior walls and the bottom. The build-up is usually caused by the hard water, which contains chemical agents, ruining gradually the structural parts of the kettle. You can wash off the layer of minerals once a weak. Otherwise, you will have to change your kettle very quick. Still, if you live in a hard water area, you will be better off if you change your kettle after maximum two years of use.