I note the related question Why do the supreme court justices have a life term period? However, that question focused on why they have life terms at all. I want to focus instead on what benefits could be provided by the current life-term system, over the concept of fixed length terms (i.e. justices only serve for x years with no repeats).
Life terms are valuable because they prevent justices from feeling obligated to vote some way in order to win a re-election. This is still a feature of fixed length terms, so fixed lengths are equally viable in this regard.
In contrast, life terms have the issue that if the president makes a "bad" appointment (in the eyes of the public), the country may be stuck with that person for 30 or 40 years, a whole 2 generations. That's a lot of time to be a bad justice and cause damage. I see this as a major downside of life terms.
I currently see only disadvantages to life terms compared to fixed length terms. So I ask - what advantages are there, if any, of the current life term system over fixed length?