Ronald Reagan was 77 years old in his final year of presidency. Mubarak (Egypt) was in power from 1981 to 2011, which means he was 83 when removed from power. Fidel Castro, similarly, was 81 (or so) when he gave up leading Cuba. Paul Biya is 81, and leading Cameroon. Howard Cooke was a leader of Jamaica until it ended when he was 90-91.

Shimon Peres (largely ceremonial position) is president of Israel.

That should give you an idea :).

Removed, please see our rules about 'in your era' questions. I will leave up the answer already posted, for your benefit.