perpetuate vs prolong

perpetuate

verb
  • To prolong the existence of (something) by repetition; to reinforce. 

  • To make (something) perpetual; to make (something) continue for an indefinite time; also, to preserve (something) from extinction or oblivion. 

  • To record (the testimony of a witness) which may be lost before a matter comes to trial. 

adj
  • Perpetual, or made perpetual; continued for an indefinite time. 

prolong

verb
  • To put off to a distant time; to postpone. 

  • To lengthen in time; to extend the duration of 

  • To become longer; lengthen. 

  • To extend in space or length. 

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