Iam a man who, from his youth upwards in the bolded section, what is the benefit of using "from his youth upward" rather than "from an early age" or "always"?

It seems that you have missed some necessary details for us to answer this so I had to look for it. Anyway, here is the answer. The given quotation above is by Herman Melville from "Bartleby the Scrivener". The benefit of using "from his youth upward" rather than "from an early age" or "always?" is that, it suggests the narrator has a strong sense of pride. Hope this helps.