Would you know the difference is your life was shortened by any unhealthy habits? (Short of doing things like base jumping without a parachute, or wearing a bra and panties to prison)I really don't think anyone knows when their time is up or how they are going to die.
Say for instance November 14 2020 is your day on the calendar. You can be a pack a day smoker or a soul who has never touched an unhealthy substance in his/her life. Guess what...November 14 2020 is your day. You never knew it, you can't avoid it. The clerk called your number...you gotta go. If you have been sick for 2 years and finally pass or a wing falls off a plane and drops through your bedroom ceiling...it is your day.
It's not a theological point of view. If it were, bad people would die young and we all know that's not the case. Your job is to take care of the here and now. If you desire, provide something for your kids when you bail out. Don't worry too much about what will happen, just take care of yourself here. I agree with moderation in everything but never miss anything if you can help it.
You can always tip the hat of your demise in your favor by going overboard with something, hasten the process, hence my comment of doing something risky to shorten your life. But if you take fairly good care of yourself and familiy and live a happy life then it isn't a wasted life when you're done living it. I say...smoke 'em if you got 'em.