Publishers working off models based on manufacturing and solicitation schedules and not what work for creators aside, some of the opaqueness in what deadlines aren't detrimental come from a lack of post mortem and review, because people don't encourage that.

Averaged out over a year or two years, or 3, do you know your layout, pencils, inks, or finished rates per day? Now were those for heavy action? Detailed Work? Slice of Life? Was it color work or B&W?

Even when working on your own stuff its good to have an idea of the scope of your project. One time someone told me their planned length for a series and I did the maths based on their prior output and asked if they were okay working on said series until the 2030s.

Their answer was an emphatic no, and we talked thru how I got there based on their own prior output. The series got retooled as a result. It is easy to get lost in the forest even if its one you're making on your own.