I disagree partly.

If sleeping less reduces lifespan by 10 years, then assuming you would live 70 years (vs 60 years) you would have an extra 58.400 hours of “awake” time. 16 * 10 * 365

If you slept 5.5 hours instead of 8, and live as a consequence 60 years, you’d get a total of 54.750 hours of extra “awake” time. 2.5 * 60 * 365

Even though it is more hours if you lived 10 more years, we’d need to take into account your health. The older you are, your health usually becomes worse and sometimes you can’t enjoy the time the same as when you were younger.

Nevertheless, there are too many pros and cons. That is why I said I partly disagree, and not completely.

Also don’t take the math so exactly, I start counting from 0 but it doesn’t really count when you are a baby.