An 18 year limit would have put Scalia out on the street a long time ago. He’s been in the SCOTUS since 1986 or for 25 years. Thomas since 1991 or 20 years. But of course this isn’t about “conservative” justices. Perry and his ilk are obviously thinking about “liberal” justices. They probably don’t realize that such an amendment would have a negative impact on conservative justices and their opinions therein.