I find the LL 4-night stays just the right number of nights I want to stay in a place. Day 1 and Day 5 are always a travel day. So you are left with 3 full days to explore a city, an area, etc. Three nights are just a little on the short side for us. You used to have 5-night deals for Rome which were wonderful. Unfortunately, these deals have gone by the wayside and we deplore this action on LL's part. We would love to return to Rome but 3 nights are just not enough, even if you have been there before. I wish LL would bring back the 5-night Rome deals.
I agree that four nights is usually the best length for a hotel stay. Since we usually arrive late in the afternoon or in the evening, the first night consists of checking in, having some dinner, and going to sleep, especially if there are multiple time zones and a long day of traveling involved. The second and third days are exploring and having fun days and then we check out on the third morning. Of course, the further we travel, the longer we would like our stay to be.