I love to write series. My Sinners Sports Romances has now come to a conclusion after fifteen books spanning two generations on the lives and loves of a football dynasty. Sales for this series simply disappeared two years ago for no reason I could discover whether it was the TikTok scam to get free books or as one editor told me, my books were too old fashioned. Young people today want highly emotional one person narrators who spend most of the books trying to solve one problem rather than third person narratives that are often funny, i.e. my books. Strange, when I first began writing I was told readers no longer wanted first person narratives, funny or not. The book I had offered at the time was Mardi Gras Madness. Eventually, it sold along with Courir de Mardi Gras with three POVS and Queen of the Mardi Gras Ball having one. They remain among my bestsellers and are easy to vend at authors' events but I haven't written anymore. Trends come and trends go, and one of those trends might kill a long running series.
I wrote four books featuring bull riders that petered out after four books. I had planned two more. They are still in the back of my mind, and some of the characters have done cameos in other books so they do live on. Currently, I am working on a ten book series, The Longleigh Chronicles, Regency set historicals that are only now catching on as I finish up book nine. I found that as I worked on this ninth book, I'd forgotten some details as I went along. Fortunately, all of my books are stored on my desk top computer (and a data stick and a Toshiba external drive). I can go back into those files and verify some character's eye color or the name of a servant, etc. that I'd long forgotten. I also keep a list of characters in a paper file with their characteristics written down just in case of computer failure. As the series expands, I need to keep track of the children born, age, and appearance. It takes a good memory and many backups to write a long series.
Then there are the things I never considered important. In Queen of the Mardi Gras Ball which takes place in the 1920s, the heroine buys several Picasso paintings that her bully of a husband hates. She loses everything to get a divorce and starts life over in another town. I forgot all about those Picassos until a reader asked me what happened to them. Gee, I don't know. Her ex might have slashed them or given them to the maid to sell. Perhaps they are still in the attic of the house on Prytania Street where Roz once lived. Interesting question. Maybe they will turn up in another unrelated book some day.
Once I finish the Longleigh Chronicles, I don't know what I will do. Perhaps some single titles. Maybe bring the Longleigh offspring into the Victorian era. I have no idea right now with the tenth book still to write. I am sure something will come to me as I cannot fathom giving up writing, successful or not.