"L’chaim is for the night they get engaged, after he proposes, and for immediate family only. So both sides can get to know each other. The vort is usually a week or two weeks later for the gantzeh velt." (source)

"Although I couldn’t understand everything the Rebbe was saying, I did understand that he was urging everyone to love their fellow Jews. And when he said l’chaim, it felt to me as if he was saying l’chaim to me alone." (source)