When you start mind map one of your projects, you can face the challenge with too long branches. Many people I know create mind maps, where one or two branches are too long in comparison with others.
I noted that often such unbalanced mind map means that its author doesn’t have a clear idea of the mind map topic. Or maybe author was keen on some aspects of the problem and forgot about other sides of it.
So, be careful, bear in mind that balanced mind map is one of the sure signs that you considered most important points of the problem.