Reply To: seuda shlishis after shabbos?

I understand that if one eats a kzayis/kbaitza before sunset one may be yotzei. My question is why do so lchatchila? It would seem that lchatchila at least most of the meal should be eaten before sunset. Also there is a machlokes whether one says retzei after shabbos when the meal started on shabbos. The Rosh holds that one does not. So lchatchila it would seem that one should not put himself in that position. Besides, why wait for the last minute? Zrizim makdimim lmitzvos.