My mum and dad both smoke
My dad is currently in hospital becuase of it mainly he smokes about 40 a day! And even though he is really trying e.g
he has given up beer and unhealthy foods. he wont stop smoking... yet.
He's stubborn and if someone doesnt want too there's no point forcing then becuase it has no effect on them at all.
This may sound a bit harsh:
If your grandad has 2 years to live then your grandad doesnt need to stop smoking, either way he's going to die soon. So he will want to enjoy the rest of his life with you, his family and relatives and of course smoking.
So there is no point trying
I am very sorry to hear this btw and spend as much time with him as you possibly can and make his last few years enjoyable.
Doctors and always right;
e.g My mums grandad smoked 80 a day and drank he lived till 97 even though the doctor said he had 4 years to live when he was 75
just goes to show.