The mentality of a four-day work week is completely different. More so for me when the day off is Friday. When Monday's off, I appreciate it that day, but the Tues-Fri week feels like a normal week crammed into four days. The only advantage of having Mondays off over having Fridays off is that everyone flakes out on Friday anyway and leaves pretty early. But when you have a Friday off, then all of the sudden Thursday is your Friday night, which means that Wednesday is Thursday. When noon hits on Wednesday and you have Friday off, be prepared to feel like you just turned around and the week's over.