dotage vs lifespan

dotage

noun
  • Fondness or attentiveness, especially to an excessive degree. 

  • Decline in judgment and other cognitive functions, associated with aging; senility. 

  • Foolish utterance(s); drivel. 

lifespan

noun
  • The length of time for which an organism lives. 

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

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

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