long-service fatigue; performance decline from working too long
Jocular term modeled on 金属疲労 (metal fatigue). Used for a person whose performance has worsened after many years in the same job or role, or for a system that malfunctions after long continuous operation.
He's suffering from long-service fatigue and has been making more mistakes lately.
This old server often crashes due to long-term operational fatigue.