That's not what half-life means. Half-life comes from radioactive decay and is the time for half the atoms in a sample to decay. After half the atoms have decayed it takes another half-life for half the remaining atoms (a quarter of the original sample) to decay. There's some fancy maths you can do to convert a sample size of 85 million with a half-life of 75 years into the time it takes for the last atom to decay but at an estimation of about 27 half-lives that's 2025 years.

Maybe that's the real problem with boomers: their multi-thousand year lifespan!!