Nobody, I repeat NOBODY, should have a job for life; unless of course, they own the company, but certainly not in government.
Every President in each of his 4 year term, should be able to put 1 Supreme Court Justice in place, and if another dies in that 4 year span, he gets 2. It should be weighted by age, and time served, with a mandatory retirement age of 67.
If the President has already replaced 1 in his 4 year term, then a 67 year old can continue on until the President is either re-elected, or loses the next election. That means no Supreme court Justice would go past the age of 70, and yes, for their service, they get an excellent retirement!