As your parents age, there are new and important topics that arise and must be discussed. There are many different types of conversations you can have with your parents and many different ways to bring up the important issues. Whether it has to do with finances, health insurance, or legal preparations these topics are usually difficult to bring up and even harder to discuss in detail.
The U.S. Department of State provides some excellent advice about communicating with elderly parents.
Eldercare.gov goes into detail about what topics to discuss with elderly parents and also gives some helpful advice on how to breach these difficult topics.
Remember to be open, honest, and NOT argumentative when discussing these topics. Regardless of the method you choose, the most important thing is that you actually talk to your parents about these issues so that they can be safe, happy, and prepared for the longest possible time.