Answer: I just wrote the answer in the explanation
Explanation: When he said this quote he was referring to the death of their dreams and aspirations rather than their physical death at 25. This quote points at the idea that from 25 to 75 a person is no longer living with youthful hope but is working to survive, awaiting their death which will come at a later age such as 75.
-This next part is opinionated but ill answer it anyways
I find faults in his idea of life and how he sees life as something that is only truly lives when you are young. As long as you are living, in my eyes you should take full advantage of your life the same way you would when young, I feel that people should have dreams goals even as they get older. While his quote may speak truth to the reality of many people's lives, I don't agree with the ideology behind it, by seeing yourself as somebody awaiting death you will forget that you are still living just as you were when younger.