I will say that early in my life I saw some extremely healthy and clean living friends killed by events and disease and I learned that we all only have a short time to live, despite the promises and absolutions we might get from doctors or priests. However, there is a difference between taking some risks and risking your life - and I guess that exploiting drugs, and sex, and rock and roll for pleasure can be in either category.
There isn't a safe zone - even complete abstinence isn't safe....
It's interesting to think what change in attitude and advice the existance of a "safe zone" would create - if medicine could really save us (allow us to live reliably much longer), if only we didn't do silly things. I sometimes think that a lot of folks operate as if that were true now, and get shocked when it turns out that it isn't. There are so many stories that start with "he used to run three times a week, never smoked and then..."