"Three times a week for the first four weeks, then twice a week for the next four weeks, then once a week for the next four weeks, etc."
Sorry. This one may roll off the tongues of thousands of chiropractors with practiced precision, but dig deeper and it's a scripted substitute for critical thinking.
Predicting the amount of care needed beyond a dozen or so visits before the first progress examination is bordering on crystal-ball-winning-the-lottery level psychic powers. Not only do many chiropractors make this stock recommendation before delivering the first adjustment, they're clueless about the patient's willingness to make lifestyle changes or take any other proactive steps to support the care they receive.
No, this is a form of bluffing. They may or may not need dozens of visits over the course of weeks and months, but declaring it up front, even when done with authority, is advanced dreaming.