Data supporting this conclusion:
Life expectancy as of 2015 for 50 year old women in the fifth quintile of income born in 1960: 41.9 years.
Source: National Academy of Sciences, The Growing Gap in Life Expectancy by Income: Implications for Federal Programs and Policy Responses (Washington, DC: The National Academies Press, 2015), Figure 3-2.
Barrett was born in 1972 so:
She’s 48 not 50.
She’s toward the top of the top quintile of income.
Age-adjusted life expectancy for people born in 1972 has been higher than for people born in 1960.
Add it all up and current life expectancy for people in Barrett’s demographic cohort is surely more than 45 years, and might be closer to 50. She could be on the Court until 2070, if man is still alive.