My parents smoked, 20 a day each, as children we hated it, hid their cigarettes etc. No matter how many mints you suck or perfume you spray you can still smell it on your clothes and skin.
My Mum gave up, then had a routine mammogram that detected she had breast cancer, but it was a secondary cancer. Primary was lung cancer, it had already spread to her brain and her legs.
SHE HAD NO SYMPTOMS, no cough, no pain, nothing. She had 2 rounds of chemo but sadly she died 10 weeks after being diagnosed. She was 62, healthy in lots of other ways, on the wii fit her wii fit age was 30.
If you saw someone going through chemo I wonder if you in turn would want to put your children through that experience of watching you hooked up to drugs to try to save you from something self inflicted.
It doesn't matter about life expectancy, maybe the final years are you fighting to breathe and watching your family being tortured by your pain.
It is still very raw for me, my Mum died just 8 months ago.