past (someone's) prime

Translations
вне (чьего-то) расцвета сил
Though he is past his prime, the singer still performs with great energy.
Хотя он уже не в расцвете сил, певец все еще выступает с огромной энергией.
Definitions
A phrase used to describe someone who is no longer as strong, capable, or successful as they once were, typically due to aging or the passage of time.