Losing a Parent to Addiction

It just dawned on me that my days with my father are numbered. He is been a lifelong chain smoker, an alcoholic, and he's suffered from drug addiction (with crack) for over 10 years. I read online that crack takes away 34 years from your life on average. My dad's 47! That doesn't even take into account the long-term affects of the alcohol and cigarettes. I'm scared that I'll have to bury my own Dad soon. I'm 15 and I'm surprised he's gotten this far without OD'ing...