elderliness vs lifespan

elderliness

noun
  • The quality or state of being elderly 

lifespan

noun
  • The length of time for which something exists or is current or valid. 

  • The length of time for which an organism lives. 

  • Some clams have lifespans far longer than those of human beings. 

How often have the words elderliness and lifespan occurred in a corpus of books? (source: Google Ngram Viewer )