long-term vs perennial

long-term

adj
  • Becoming evident after a relatively long time period. 

  • Extending over a relatively long time period. 

perennial

adj
  • Lasting or remaining active throughout the year, or all the time. 

  • Appearing or recurring again and again; recurrent. 

  • Continuing without cessation or intermission for several years, or for an undetermined or infinite period; neverending or never failing; perpetual, unceasing. 

  • Of a plant: active throughout the year, or having a life cycle of more than two growing seasons. 

  • Appearing again each year; annual. 

noun
  • A plant that is active throughout the year, or has a life cycle of more than two growing seasons. 

  • A thing that lasts forever. 

  • A person or thing (such as a problem) that appears or returns regularly. 

How often have the words long-term and perennial occurred in a corpus of books? (source: Google Ngram Viewer )