I first heard of 24 hour writing contests some years ago, and took part a few times. (Even got an honorable mention once, though the story has since been trunked and lies unused, unpolished, unsold) In those days I was much into flash fiction.
Since then, I have moved to longer short fiction, that is, fiction that dares to go above 500 or even 1000 words. My story lengths now are typically above 2000, sometimes going right up to 6000 (then I struggle to get them down). So I had stopped thinking about these contests.
But last month, I decided to use a contest to just give my muse some variety. So yesterday, I took part in another of the 24-hour contests, my idea being to just have some fun (in a masochist way). Well, it was fun, and maybe I should do it oftener. It gives me practice of saying no to my editor-mind, and I think my muse gets a chance to feel pampered
Of course, if I want more fun, I should try twitter-fiction which is now getting to be a genre of its own. What! Not able to write a complete story in 140 characters? What sort of writer are you?