Question: In the *Supernatural* universe burying your photo with some hoodoo items at a crossroads summons a demon, said demon offers you a deal normally offers you a deal.

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> "You can have that thing you wanted, and in exchange for your soul in ten years.
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What if you die early? Does your soul go to hell anyway? Do demons prefer a soul ripped from its mortal coil, or does it not matter to them?

Answer: 
The demons don't promise you'll live for 10 years, unless that's specifically part of the deal. But as can be seen in a recent episode, they strongly discourage their own from cheating and killing those with whom deals are made... it's considered bad for business.
They would be sent to Hell early if the demon holding their contract takes their soul. Most of the time that's the case. 

But sometimes, however, if the deed the crossroads demon promised as part of the deal is not fulfilled and the owner of deal dies, then the soul would not be taken to Hell.