Messages should ALWAYS be your last resort. One of the great benefits of CoConstruct is how it lets you group related information together. However, messages are just a running list, without any real organization.
First, try and see if you should instead be adding a comment to an existing question, selection, to-do item, or warranty item. This will help you keep related thoughts together and make them easier to find later.
In the end, messages are best suited for quick items like scheduling a walkthrough or wishing a client happy birthday.