Life expectancy in US is 79. The person is 60 years old. He/She makes $100K annually.
2*(79-60)*$100K = $3.8M
Based on your formula, He/She should have 3.8M in retirement saving. Most of people can not achieve that. Plus, the 3.8M asset will produce $152K annual retirement income which is 50% more than the working income. It is nice life.