Probably a bit younger than that like 75-80, but 85 should the maximum point. You see, old people are old. Scientifically, that means that person kind of lose brain cells. That does not they become dumb or they can't comprehend anything. How I think of it is, old people can't reach their maximum performance as they used to. I mean, some old people age amazingly well. But that's just SOME, and I'm talking about MOST. When you have an 85 year man sitting in a chair or whatever she's doing, she can't do as well as someone who's in his 40's. That's how I think of it that way?
Supreme Court justices should retire at age 85, because they could pass on or get ill during their term of office. The elderly should not have to serve in the government, because we need them to be healthy and stable. They must be able to report to their jobs like anyone else.
This may be an unpopular answer, but yes, I do feel Supreme Court justices should retire at the age of 85 or at least be required to take some sort of lengthy test to determine if they are still in the right mental state to be able to make the right decisions in the court.
I do not think that there should be a mandatory retirement age for Supreme Court justices. I don't like the idea of how that might change Presidential campaigns. Knowing ahead of time that a certain amount of justices will be forced out during one's administration (that they could replace with people who share their ideology) could lead to all sorts of problems and corruption.
I believe that the Supreme Court should not have a retirement age because there are many ideas and opinions that older people can give to the United States. However, I support an oversight provision where if the Justice is unable to complete there job as a Justice, there is a body of people that can offer the Justice to walk away or if they refuse to have another body of people that can vote.