Three projects a year is a capacity decision. There are two of us, some excellent collaborators, and a finite number of days on which we are useful. We would rather account for that honestly.
A project means a substantial identity or website commission. Small repairs for existing clients do not turn into secret fourth projects. They have time reserved for them, mostly in winter.
The limit makes room for research, proper implementation, and the awkward weeks when an idea has not become good yet. It also makes room for holidays. We do not believe this last point needs a theory.
If the calendar is full, it stays full. There is no premium queue and no persuasive exception. You can write about a later year. You can also work with somebody else. There are good people doing good work at other speeds.