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: 
Yes it happens in one episode. Crowley gets furious with a demon who had made this kind of deal. He actually says:

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> *This isn't Wall Street, this is Hell. We have a little something called integrity.*
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[Link to YouTube](http://www.youtube.com/watch?v=nNAvGfh-Uvg)

If the human who did the deal dies before the deal time, the owner of the contract decides what to do; usually, they take the soul.

However the contract could also have a clause for such an eventuality.
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.