Why did neither Sam nor Dean become demons?

[NishiNoMajo]

We know that the first demon, Lilith, was created by Lucifer himself. In 3.09 "Malleus Maleficarum" we also learn from Ruby that all demons were once humans who lost their humanity after being tortured in hell (much like Orcs in LOTR that were originally elves). However, we don't know how much time and how much torture it takes for a human being to become a demon.

Since next episode is dealing with Sam's hell trauma, I have been wondering why neither him nor Dean turned into demons. Dean spent 30 years being tortured in hell and for 10 years, he tortured other souls himself. This will haunt him for the rest of his life, but he didn't become a demon. Sam spent about 180 years locked in a cage with Lucifer himself and suffered unimaginable trauma, which is probably more than Lilith ever endured. But still Sam did not turn into a demon. Why?

Do you think it is because the boys are "better" people than the other souls suffering in hell (also since Dean was referred to as a righteous man)? Or would they have been turned into demons if they were tortured for a longer period of time? Or is it simply a plot hole?

[Aeryn]

That is a very good question!!!

Frankly, I think the reason is the writers didn't think about it.

[Lostcause]

You'd probably have to endure quite a long time of mental and physical torture to turn into a black smoke monster.

Just ask the evil dude from Lost!

[AntiArbitrator]

I think they were not in hell nearly long enough to forget what they are. Apparently it takes a long time for people to become vengeful spirits like ghosts and maybe hundreds of earth years to forget and turn to black smoke. We saw John W's spirit but it was not demonic.

I'm pretty sure in another thousand years Dean would have been a bad-ass demon. I would still love him though.

[SoCal]

Maybe because they were both pulled out of Hell by an angel.
I dunno, but good question....one of many the writers of Supernatural have never explored.