Wiktionary
autumn years
n. (context literary English) the later years of one's life, especially after one has finished their career
Usage examples of "autumn years".
That he succumbed in his autumn years to temptation, I can understand and in truth I pity him, for despite his great age and wisdom it seemed to me that he still thought of the woman with affection and regretted to the end of his life any harm that might have come to her because of his weakness.