If Tai Chi is so beneficial for you then why don't all masters live to like a hundred? Or do they?

It's not just about living to be a hundred, but about quality of life as well. Some of the Tai Chi Masters I've seen are young looking and pretty spry for 80 year olds, they are even more agile and have more vigor than non practicing 60 year olds. Of course being a Tai Chi master won't help if your body is subjected to bad vices like excessive smoking, alcohol and bad diet. The Yin and Yang principles of Tai Chi dictates that you live a balanced life of moderation, not extremes and excesses. That's something that's getting harder and harder to do in today's high living society.

Actually they do. Not just Tai Chi masters, but all CMA stylists in general. There are scientific studies proving the benefits of Neijia (internal) styles, primarily chi kung and meditation.

Some masters live a long time. Another way to look at it is how well you will be the rest of your life. A good life style will add to your healthy and productive years and help you ward off debilitating diseases.
How do you want to go out.... Good exercise every day and good food habits and you are likely to die of old age sitting in your rocker.
Live like a slug don't do what is best for your system and go out when someone has to pull your plug.

depends on their lives style... just taking tai chi wont let u liv fer like 99 years...

The Internal Arts are known for extending life. They not only live long but can also rupture your internal organs with a strike.

genetics gets them in the end