It's funny to me (and I've done it too) that people mis-remember how Roy's finite life-expectancy plot worked.
It wasn't a feature; it was a bug. The company marketed it as a feature, but in reality (before Rachael, maybe) they didn't know how to build Nexus-6 with more than a four-year life expectancy. When Roy finally tracks down his creator and demands he remove it, Tyrell admits that he can't.
```
Tyrell: You were made as well as we could make you.
Roy: But not to last.
```
It's the realization that his own creator, despite all the marketing hype, isn't a god, but just another flawed mortal... that the two of them are fundamentally equal creatures in this mad universe... that pushes Roy past the edge into madness and eventual redemption, when he realizes that in the face of a universe so cold and uncaring about the life within it, it's only life that can care about life. All of it, in all its forms.
It wasn't a feature; it was a bug. The company marketed it as a feature, but in reality (before Rachael, maybe) they didn't know how to build Nexus-6 with more than a four-year life expectancy. When Roy finally tracks down his creator and demands he remove it, Tyrell admits that he can't.
```
Tyrell: You were made as well as we could make you.
Roy: But not to last.
```
It's the realization that his own creator, despite all the marketing hype, isn't a god, but just another flawed mortal... that the two of them are fundamentally equal creatures in this mad universe... that pushes Roy past the edge into madness and eventual redemption, when he realizes that in the face of a universe so cold and uncaring about the life within it, it's only life that can care about life. All of it, in all its forms.