A 50-year-old man born on July 1, 1960 currently has a life expectancy of 81, according to the SSA's new life expectancy calculator, released last week. Once he makes it to age 67 his live expectancy grows to 84.4 years and if he hits 70 the average life expectancy is 85.3 years.
This is because the elite very long lifers progress through their years.
How long am I likely to live?

Overall, social support increases survival by some 50 percent, concluded the authors behind a recent meta-analysis.
The benefit of friends, family and even colleagues turns out to be just as good for long-term survival as giving up a 15-cigarette-a-day smoking habit. And by the study's numbers, interpersonal social networks are more crucial to physical health than exercising or beating obesity. Of course improving health outcomes is even more successful if you give up smoking too!

Specifying treatment: This comes under the heading of Advance Care Planning, which is a way of letting your relatives, professionals know what you wish to happen as end of life gets near for you. Normally this does not need legal sanction. An exception is where you are definite you would NEVER want a certain treatment even if your life depended upon it. In this case you can make an Advance Decision to Refuse Treatment which has legal force should you become incapable of decision making. Web-sites such as macmillan.org.uk; cancerresearchuk.org, nhs.uk, and gov.uk have information about these.

These are decisions that depend on your personal circumstances and your expressed or recorded wishes. You have the right to refuse any medical intervention or admission if you want to do so. As long as there is capacity in the venue in which you elect to die the staff advising and caring for you will take your wishes into account.

See for example the Co-op web-site: “Choosing a coffin
Although traditional wood coffins are still the most popular type of coffin, alternative materials are also available. Coffins made of bamboo, wool, wicker, cardboard, willow or recycled materials are becoming more widespread.”

You can do everything yourself if you decide to. It represents a lot of work, but it is achievable.