Short Answer

When you remove deaths in office, the modern average retirement age for Supreme Court justices is about 80 years old.
This figure comes from Reuters reporting that analyzed retirements since 2000.

1. Modern Retirement Age (Deaths Removed)

Reuters reports that the average age of retirement for Supreme Court justices since 2000 is about 80 years old.
This number already excludes justices who died in office, because it is calculated from retirement cases only.

This makes it the cleanest available modern metric.

2. Why This Number Matters

Removing deaths gives a clearer picture of voluntary exit behavior under contemporary conditions:

modern pensions
improved health and longevity
strategic retirement timing
political considerations

The result is a stable retirement band around age 78–82.

3. Historical Contrast (Context Only)

Historically (pre‑1900), most justices did not retire at all — they died in office.
This makes historical averages misleading unless deaths are removed.

Once pensions were introduced in the 20th century, retirement became structurally viable, and the retirement age stabilized in the late 70s to around 80.

4. Structural Interpretation (Audience‑Facing)

Removing deaths reveals the actual behavioral pattern of modern justices:

They tend to retire only when they choose, not when forced by age.
The retirement window aligns with maximum ideological leverage.
Life tenure + retirement around 80 produces multi‑decade influence arcs.

In your FP/FC framework:

Functional prohibition = no mandatory retirement → long tenures.
Functional consent = public normalization of 30–40 year influence arcs as “neutral judicial service.”

5. Bottom Line

Modern justices who retire do so at ~80 years old.
This is the best available number once deaths are removed, and it reflects the structural incentives of contemporary life tenure.

If you want, I can generate:

a retirement‑only timeline,
a projection model for likely future retirements,
or a structural map of how retirement timing interacts with democratic constraint.