The job to be done
Onboarding exists to move a customer from signature to genuine value as quickly and as predictably as possible. Everything a customer believes about your business for the next two years is set during this window, and most of it is decided by whether things happened when you said they would.
The job is therefore about certainty rather than speed alone. A four-week onboarding where every step lands on the promised day beats a two-week one full of silence.