Board Thread:Questions and Answers/@comment-80.132.99.68-20150329114408/@comment-918376-20150829132636

Just to note, the first five volumes were published one-after-the-other so quickly because Mamare already had it written some time beforehand. Between volumes 5 and 6 was when he had to start working on "new material".

So most accurately, Mamare publishes around 1-2 volumes per year, and there's around five more to go after volume 10.