'Lifetime' in the Bible

I know that there is nothing better for them than to rejoice and to do good in one’s lifetime;

For who knows what is good for a man during his lifetime, during the few years of his futile life? He will spend them like a shadow. For who can tell a man what will be after him under the sun?

I have seen everything during my lifetime of futility; there is a righteous man who perishes in his righteousness and there is a wicked man who prolongs his life in his wickedness.