Why am I still living?

This is a question I am frequently asked by older persons at the end of their lives. It is usually a legitimate question. I often answer that we like having them around, and that God is not done using them on this earth. I feel that older persons offer a lot of wisdom and love if we take the time for them. It’s also not why are we still here on earth, but how are we going to live out the rest of our lives.
The Apostle Paul also speaks more eloquently than I can, when he writes from jail in 
Philippians 1:20-26.

I eagerly expect and hope that I will in no way be ashamed, 
but will have sufficient courage so that now as always 
Christ will be exalted in my body, whether by life or by death. 
For to me, to live in Christ and to die is gain. If I am to go on
living in the body, this will mean fruitful labor for me. Yet 
what shall I choose? I do not know! I am torn between the two: 
I desire to depart and be with Christ, which is better by far; 
but it is more necessary for you that I remain in the body. 
Convinced of this, I know that I will remain, and I will continue
with all of you for your progress and joy in the faith, so that 
through my being with you again your joy in Christ Jesus 
will overflow on account of me.