Well, in your estimation, you wouldn't. A person who ends up damned has always been so, even if they appeared to walk on the path of righteousness for a time.
Read 1 John. He tells us that if we walk on the path, we will have our sins removed. That means that if we do not do so, we will be guilty. Someone could buy into this "Once Saved Always Saved" notion and believe themselves one of the "elect." But if they fall into sin and die that way, they will go to hell. Regardless of what they believed earlier.
The poiint is that it's nice to know that those "saved" in the end are a class of people that God has known and chosen. But for our lives, we best be concerned with walking in the light.
SD