In all human beings, the brain works faster than speech. What you are saying is that your children talk a lot. We worry when they don't and we worry when they do!
To come to the implication of your specific observation: Children often talk in order to get the parents to attend to them. You could suggest that they talk in turn and to convey something. Listening is also important. You could invent a Silence game when they are absolutely still for two minutes. You could read out a story and ask them to tell it back to you. In that way, their listening skills will also be developed. You could have them play Chinese Whispers and have them see how messages get distorted. Soft music can be played as the children are winding down for the night, so that they quieten down and sleep well.