Definition of "all the while"
all the while
adverb
not comparable
(idiomatic) At the same time as, usually over an extended period.
Quotations
The good fortune which attended him throughout life may have been partly owing to this cause as well as to his undoubted valour, for though he never lost a battle, nothing is more astounding than his imprudence and the easy confidence with which he trusted Somerset, Warwick, Montague, and others, all the while they were betraying him.
1889, Leslie Stephen, Dictionary of National Biography, page 82