It is important to remember that our forefathers never accepted age as an excuse.
Perhaps that is one of the reasons that Abraham was circumcised when he was ninety-nine years old – so that no one would be able to claim advanced age as an excuse to avoid starting on a new path.
That person would simply look at Abraham, who at ninety-nine made a new start from the same place where an eight-day-old baby begins.
–Rabbi Adin Steinsaltz