End Life Tenure for Supreme Court Justices?

This post at Law.com previews a book and corresponding law review article arguing for 18-year fixed terms for U.S. Supreme Court justices.  The premise seems to be that the founders could never have contemplated the long durations of most recent justices’ tenures, which arise from increases in life expectancy and retirement age.  The post has lots of links and some tidbits of info about the service of Supreme Court justices.