This is one of the common points of failure in the cooling system.
So is the temperature sensor on the lower radiator hose (the o-ring, specifically).
There are a few main reasons why many believe that replacing everything in one go is the best way... After you buy all the parts that did or most likely will go bad, you've bought most of the system. And it's better to do it once and be done.
Unless, of course you like taking it apart....