When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return. (Leonardo da Vinci)
Should "When" not be there, because "once" itself will be able to lead a subordinate clause?
Should there be "on" between "walk" and "the earth"?
Should "there" be "where" instead, so "where you have been, and where you will always long to return" becomes the object of prep. "for"?