Novel vs. Novella: A Question of Time

.

So Blood of the Falcon has been out for a month or nearly and checking the Kindle sells daily has resulted in my overwhelming astonishment. The actual numbers are not the point; the point is that a novel so fat that it has to be broken into two volumes keeps selling steadily, when a skinny, convenient, fast read like Mists of Blackfen Bog stagnates at tiny numbers. In comparison, I've marketed Falcons far less than Mists and the novel's sells keep rising.

Now, I have discussed this question with a writing friend and we cannot come to a satisfying reason why, in our fast-paced culture in which people with shortening attention spans are expecting quick results, that short stories and novellas would be largely ignored while novels, that take up so much more time, energy and devotion to reach the end, would continue to sell like hot cakes. The best I can come up with is that readers who are following this trend are those bookworms who prefer long-term commitment to a character and a situation rather than a one-night stand with a briefer story. Any other theories out there?

From a writer's standpoint, then, considering all the numbers, is it more worth my own time and energy writing full-length novels rather than novellas? Novellas are hard to sell, few markets exist that accept them. Yet fewer publishers take chances on unknown novelists. So the results will most likely end up in a self-publishing venture.Which leads me back around to while novels sell better, I can have more novellas out on the market in far less time, but if few are buying them (aka reading them), why bother? As you can see, I'm torn. Any opinions or encouragement or personal experience to share?
.