Yes, Yorkies have a longer life expectancy when compared to many other breeds. My Noah lived to be 18 years old. He was never really sick until he was 16 or 17 when he got cancer.
Each pure breed dog comes with a limited gene pool and certain genetic markers carry a higher risk of some diseases or disorders. Some examples are, Bull dogs are pron breathing and skin problems, Labs bad hips, Dalmatians deafness, Cockers mood disorders,Boxers cancer, King Charles water on the brain, Yorkies bad knees etc.
As you know good breeders have their dogs tested for genetic diseases. But not all problems can be predetermined. Mixed dogs suffer from the same diseases and problems that pure bred dogs do. But who keeps records about mixed breed dogs ? Who does research for medium sized Watchmacallit that gets a bad heart valve ?
My suggestion is to choose the best breeder you can find, and get a dog from them. Every one and every thing dies at some point in time. All we can do is make an educated decision.
We can not let fear of what might happen keep us from loving and sharing our life with people or Yorkies.
God bless, and best wishes Teresa and the
Gang