This is an interesting one. There is only one place in the Bible that speaks of retirement.
The Lord said to Moses, "This applies to the Levites: Men 25 years old or more shall come to take part in the work at the tent of meeting, but at the age of 50, they must retire from their regular service and work no longer. They may assist their brothers in performing their duties at the tent of meeting, but they themselves must not do the work." Numbers 8:23-26
Nice. Age 50 would be a great age to "retire." But, notice they are still to assist their brothers.
The real idea, I think, is that I am here for a reason. I have a purpose to influence others for Christ, by word, example or deed. So, what retirement really means in the Christian sense is not to give in, give up or quit working for Christ even when it is hard and no matter how old I am.
Therefore, since through God's mercy we have this ministry, we do not lose heart. 2 Corinthians 4:1
Does this mean I need to tell every single person I meet every day that Jesus loves them? Does it mean that I need to run off to outer Mongolia and be a missionary? It could be those things.
But, more than likely it is the fact that I have 4 young eyes watching my every move. I have 4 little ears listening to my every word. Yes, I have influence and interaction with 100s on a daily basis through Facebook and other social media and I have face to face interaction with several dozen a day. But, the ones that really count are right under my own roof.
However, I consider my life worth nothing to me; my only aim is to finish the race and complete the task the Lord Jesus has given me--the task of testifying to the good news of God's grace. Acts 20:24