What is the most years a person can sevrve as president?

This is like a trick question. The maximum "number of years" one person can serve as President is unlimited. It is NOT 8 years. The 22nd Amendment states that no person may be "elected" more than twice. It says nothing about the number of years a person can serve. It also provides that no person who acted as President for more than 2 years during a term in which some other person was elected President may be elected more than 1 time. So, consider this situation: A vice president becomes president on the death of the president and serves exactly 2 years. Since it is not more than 2 years, he is able to be elected twice. That's 10 years. After that suppose he serves a vice president again and again succeeds to office on the death of the new president. Unlikely, yes, but theoretically it is not prohibited.