Medicare beneficiaries who are near death are the primary cause of large medicare payments.

It is not true that Medicare beneficiaries who are near death are primary cause of large Medicare Payments. Medicare is the federal government program that provides health care coverage. This program is in part funded by Social Security and Medicare taxes you pay on your income, in part funded through premiums that people with Medicare pay, and in part funded through the federal budget.

The concept of internal human stability which is also a central concept of human physiology which you're talking about/asking a question about would be homeostasis. By a homeostatis we're talking about a very narrow interval of functioning in which people function best and have optimal working efficiency.