There's no set time for how long it should take to write a story, it depends so much on how long it is, how involved it is, and just how well the writing goes. I generally have a rough outline for my stories, but sometimes they go like woah and other times I'm just plodding painfully along.

I will say that I've felt, recently, that my writing has suffered because of having deadlines, but that's also more about me signing up for too much as well. But I do think it's important to write for happiness' sake and not feel like you HAVE to finish this.

Not sure if that was very coherent or helpful... ;-)