My parents are 65 years old and
My parents are 65 years old and I am only 16. How can I extend their lives?
Richard Muller, Children and grandchildren are the greatest source of joy in life.

You are already doing that. The very fact that you ask such a wonderful and thoughtful question means to me that you will continue to give them the joy that will make them want to live on and on.
The key is that they love you, and they expect and know that you are at an age when drifting away from them is natural. They are anticipating missing you. Just a little bit of effort on your part to stay in touch can mean a lot.
Any indication that you continue to love them will be cherished. I recommend a lot of little things rather than one big thing. Maybe you will soon be getting a job and moving out; maybe you will be off to college. If you move away, try this old-fashioned trick:write them letters. Letters have the amazing quality that they endure, they can be read and re-read. Make sure they know what you are up to. (I remember vividly my mom’s excitement and worry when I told her I had a girlfriend. She noticed—which I didn’t—that it was the first time I had ever said that, even though I had had others. She correctly predicted, but didn’t say, that I had found my permanent one.)
Visit more often than you have to. (More than just Thanksgiving and Christmas.) Recognize the fact that they will always (despite themselves) treat you like their little kid. Don’t be bothered by that; be amused when they tell you that you should wash your jeans. Treat them with respect even when they are becoming unreasonable. Show them that you love them by doing little things, such as washing the dishes when they don’t ask.
But I don’t think you need this advice. Thinking to ask that question shows a great love and concern, and that’s the key.
▌VOCABULARY:
anticipate: see (what is going to happen or what needs to be done) and act accordingly 预见到(要发生的事或需要做的事)而采取措施:
A good general can anticipate what the enemy will do. 善战的将领能预知敌军动向而作好战斗部署。