My maximum that I held for a total of 3 days was 15 chapters. However, that was clearly not sustainable in any way. Technically, I could probably do 10 chapters per day consistently if I was a full-time writer which would be a daily chapter for 10 books, but we all have lives so again that would just not be very sustainable for a long term type of scenario.
So short term yes that is doable depending on the author, but anything that would last more than a week is highly unlikely. I agree though that if there was a chapter outline and character breakdown and everything already set up, it would be much easier but writing so many chapters daily does catch up with you health wise eventually which is why you see some authors only juggling 2 and maybe entering a competition with a 3rd but will not do any more than that until one of the three are completed or the traction drops and there is no reason to continue (which is also why you see some novels that seem popular like 1+ million views getting dropped so frequently on here).
In general, authors do not make very much so there is no reason to put yourself in a health risking situation or drastic lifestyle change (literally waking up and writing all day then going to sleep and repeating the process for months at a time). Sure the top 1% that make a livable wage and then some can possibly change that, but the top 1% does not mean that every additional book will continue to do as well or better compared to the one that is succeeding as far as profits wise. Plus once the hype on said popular book dies down, your income begins to dry up to some degree.