flash in the pan vs perpetual

flash in the pan

noun
  • A career notable for early success not followed by significant accomplishment. 

  • A transient occurrence with no long-term effect. 

perpetual

adj
  • Set up to be in effect or have tenure for an unlimited duration. 

  • Continuing; uninterrupted. 

  • Lasting forever, or for an indefinitely long time. 

  • Flowering throughout the growing season. 

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