The following quote is from "American Caesar: Douglas MacArthur 1880 – 1964":
[MacArthur] was ambushed by two guerrillas. A bullet tore through the
crown of his campaign hat and into a sapling behind him. Drawing his
.38 pistol, he shot both ambushers. An Irish sergeant inspected the
bodies, saluted the twenty-three-year-old officer, and said "Begging
the lieutenant's pardon, but all the rest of the lieutenant's life is
pure velvet."
I've never heard this expression ("the rest… is pure velvet") and don't understand how it's supposed to apply here. "Velvet" is sometimes used as a synonym for "smooth"; was the sergeant suggesting his life would go smoothly? That makes little sense, as "you're living on borrowed time" might be a more appropriate given that context!
Best Answer
I did a little Ngramming and found a few usages which probably explain the term: https://www.google.com/search?q=%22will%20be%20velvet%22&tbm=bks&tbs=cdr:1,cd_min:1928,cd_max:1988&lr=lang_en
Several of the uses on this page say that some result "will be velvet", implying that it's a "bonus" for some trivial action, once other expenses are covered.
Eg, The saving in time and nesting material will more than pay for the gypsum. The extra price you get for clean eggs will be velvet.
I'm vaguely recalling hearing this idiom from time to time, though it's pretty much passed out of use. The expression "the rest is gravy" has largely supplanted it (but "gravy" wouldn't sound nearly as good in your biography).