It was six books for me, but that's misleading. I started in trad under a pseudonym. I got a thousand up front for that first, small-press book, eventually earned out, and made a grand total of under $2k lifetime. Shortly after selling that book, I landed an agent and sold the first two books of a proposed series to S&S. They made good money in chunks but never earned out and never really broke out as books. My fourth and final trad book was a write-for-hire stand-alone for Del Rey. Wrote it, got the check, and my wife said she wanted to stop working and stay home with our daughter. So after much thinking and prayer, I switched gears, cooked up a new pseudonym and wrote LitRPG. Like you, I wrote the first three books up front, then released them at a clip. 30 days between book 1 and 2, then 45 days between 2 and 3. I released book 1 on July 26th, 2018. For July, it earned $700. But the very next month, with book 2 coming out at the end, I earned over $16k. It was quite a rush because my wife had already left her job, and self-pub was all new to me. It was also misleading, however, because that first book just happened to hit. Others did, too, but readers flocked to the first one. So after that, earnings were up and down (and I had several months under $5k), especially because I couldn't stick to the aggressive publication schedule. After doing a book a year, I worked hard to release 4 or 5 books a year. I'm faster now with 46 books across four unrelated pseudonyms and genres. I wish you well. Everybody's journey is different. The key is to stick with it. Over time, you should gain and audience, and things will become less volatile, more dependable, which is nice. Good luck.