The short answer is never. The current generation of senators will make their decision on his nomination and the current generation of voters will decide how they feel about that decision in the next election, but—if he is confirmed—the next generation of voters will have to live with his influence as long as he wants to serve. When citizens born this year have their first chance to vote in 2036, if Brett Kavanaugh is sitting on the Court, he will just be hitting his stride at 71. Of course, he will be sitting next to Ruth Bader Ginsburg, celebrating her 103rd birthday.
Out of the controversy surrounding the politicization of the Supreme Court, a group called Fix the Court has been calling for an 18 year term limit for justices. They propose that when the current justices retire, all new justices be appointed for an 18 year term. Eventually, each president would get to nominate two justices, one in the first year of their term and another in the third. Having an 18 year term would provide a regular rotation, insulate the court from political pressures and eliminate the practice some justices waiting for the “right” president before retiring.
Fix the Court focuses on the term limit proposal as a way of restoring balance to the court, but it dovetails nicely with democracy for the next generation of voters. When the U.S. Constitution was written, the average life expectancy was 36, so the natural passing of justices insured that each generation could have influence on the composition of the Supreme Court. That is no longer the case. By giving lifetime appointments, we are tying the hands of the next generation. It may take a constitutional amendment, but the idea of term limits for Supreme Court justices is an idea whose time has come.