I update when I have more to update with. Depending on the story, that's historically been anywhere from every day to every few months.

Some fandoms are really impatient, so I don't post WIPs there. Old fandoms, though, where people have been looking for new material for years anyway? I don't feel like making them wait until I'm all the way done. And kink memes seem to like even small updates as long as they're regular.