Objections during opening and closing arguments are pretty rare. At least in Arkansas, the jury is instructed that 'statements of counsel are not evidence,' and the attorneys have much more leeway during arguments than they do during direct and cross examinations.
I don't speak for anyone else, but when I play defense, I've always found it difficult to pin down my closing argument until I've heard the plaintiff's closing. I might have a rough framework, but I spend the time during their closing making notes, so that I can be sure to respond to the points they make. Sometimes, that means I come across as meandering. Others, it looks like I know what I'm doing.