If it's the first Wednesday of the month, it must be time for another Insecure Writers Support Group post. You can learn more about the group here.
One of the things I've been hearing lately on my self-publishing e-mail group is that it can take at least five books in one genre, subgenre, or series for an author, especially a self-published one, to become established, or at least start to see steady sales. (I looked on the Smashwords blog and Authorearnings.com for evidence to support this, but I didn't find any. Maybe I'm looking in the wrong places, or maybe this number is only based on anecdotes.) Of course, some authors may hit it big with their first book, while others may write lots of books and never develop an audience. But aiming for five books will definitely help develop your craft and make it easier to market your work. For example, if you have five books in a series, you can set your first book to free or a bargain price to attract readers and place ads. You can also bundle books together to make them more attractive.
No matter how many books you have out, perseverance is necessary to succeed as a writer. It can take a long time to write a book, and it can take a longer time to develop a fanbase. Keep writing and keep publishing even if nothing seems to be coming of it. Every book or story out in the world brings you closer to your goals.
How many books do you think is the right length for a series? Do you like open-ended series, or do you like them to end after a certain number of books? Will you read an unfinished series, or do you prefer to wait until all the books are out? Feel free to answer in the comments.