勤つとめ盛ざかり

noun

prime of one's career; height of one's working life

Refers to the period when one is most active and productive in one's career, typically middle age.

• 彼かれは今いまが勤つとめ盛ざかりで、毎まい日にち忙いそがしく働はたらいている。

  He is now in the prime of his career and works busily every day.