mature vs not as young as one used to be

mature

adj
  • Brought to a state of complete readiness. 

  • Profound; careful. 

  • Fully developed; grown up in terms of physical appearance, behaviour or thinking; ripe. 

  • Suitable for adults only, due to sexual themes, violence, etc. 

verb
  • To attain maturity, to become mature or ripe. 

  • To make (something, e.g. fruit) ripe or mature. 

  • To make (someone) mature. 

  • To proceed toward maturity: full development or completion (either of concrete or of abstract things, e.g. plans, judgments, qualities). 

  • To proceed toward or become mature or full-grown, either physically or psychologically; to gain experience or wisdom with age. 

  • To bring (something) to maturity, full development, or completion. 

  • To reach the date when payment is due. 

not as young as one used to be

How often have the words mature and not as young as one used to be occurred in a corpus of books? (source: Google Ngram Viewer )