ISWG: Quantity Versus Quality

I'd hate to complain that I don't have enough time to write, as I am well aware that a true writer makes time to write, and that I try to do. However, I often find myself disappointed at the word count I crank out in a week: quite low, usually less than 1000 words a week, when ideally I would like to get at least 1000 each day.
I'm disappointed, that is, until I actually read the words; then I'm not quite as disappointed anymore. Those measly 1000 words are pretty good words, if I do say so myself. I think this is because when I am not engaged in the physical act of writing, I spend most of my time--practically constantly--pondering the ins and outs of the story; I write the whole story in my head before I put the words onto the paper, so even though it takes a long, long time, it's essentially complete and as I pictured the story when I finally get down to writing it.

I'm a slow and steady type of writer. I wish I could amp up the quantity I write, but then again, is it so bad to take ten years to write one little novel if it turns out fantastically? I do believe in quality over quantity, but should there be a happy medium?
Peace, Aimee