Once you become a parent you are always a parent. Your relationship with your children changes over time . The same is true of the child of God. I have fought the good fight, I have finished the race, I have kept the faith. Paul didn't feel he was finished with his service until his life was over.
Christian service has no retirement age.
It is a marathon run, not a sprint. A retired Christian worker is not only an oxymoron . . . Moses didn't feel qualified, but God used Him. Jeremiah felt he was too young, but God used Him. Saul felt unqualified to be King, but God used Him.