elderly vs past one's prime

elderly

noun
  • An elderly person. 

  • Older people as a whole. 

adj
  • old; having lived for relatively many years. 

  • Of an object, being old-fashioned or frail due to aging. 

past one's prime

prep
  • No longer in an ideal condition. 

How often have the words elderly and past one's prime occurred in a corpus of books? (source: Google Ngram Viewer )