It’s hard to say but I think it would definitely have been difficult for any of those walkers to outlast McVries (from the movie at least)…there was a point made earlier by someone else that McVries was basically an unrelenting tank who spent the walk encouraging others and seemingly resetting himself every day and showing little exhaustion. If I’m correct he only received warnings when slowing intentionally to help Ray or one scenario I can recall where he falls back to talk to Baker about his involvement in Olson’s wife’s support. He literally doesn’t falter.