I disagree with the first sentence because songs are an easy way of getting the grup engaged in the activity. What we have to do, as a teacher, is to increase the difficulty of the song, they have to see them as a challenge.
I agree with the first part of the second sentence. It's good to review the previous class but i disagree with the second part. It's not necessary to finish lessons with a song. You can finish lessons with a game, a tongue-twister or another TPR activity.
According to the third sentence, it's very important to create extra activities for fast finishers but it's also useful to adapt the material for the students with special educational needs. The teacher has to take into account all the diversity of learning that all his pupils have.