My mom smoked 2 packs a day until at least her mid 40s, after staring at age 10. I have no idea when she stopped because I went almost no contact after moving out at 17.

She appeared in excellent health until a massive stroke at 77. Barely recovered then died of the flu at 80. This is after years of going vegan and walking 10+ miles per day.

Mind you, she was antivax, trending heavily towards anti medicine and anti science. As a former very well regarded biochemist.