Why do you think Eddie asked his wife to change back to the age when he last knew her and not the age when they were first married, even though they were dancing at their wedding?

Eddie wanted marguerite as he'd last known her.... so, he could move on and feel as if he belonged.

When he moved his head back, she was 47 again, the web of lines beside her eyes, the thinner hair, the looser skin beneath her chin. She
smiled and he smiled, and she was, to him, as beautiful as ever, and he closed his eyes and said for the first time what he'd been feeling from
the moment he saw her again: "I don't want to go on. I want to stay here."