The very first activity we began when forming the User Experience organization was a throughout research and design process to create official user personas, dubbed "The Persona Projects".
Why was this significant? For years, Teradata built products for one target persona (DBAs) and engineers gather requests and took them as requirements with no true UX process. We shifted the entire culture to User-Centered-Design (UCD) completely centered on real personas built from real customers.
The right balance
Our UX team originally started with 17 personas, but as our research went on we realized that many of the personas were duplicative or unnecessarily segregated. We widdled the core user personas down from 17 to 6, and slowly started building back up from there.
How much research is enough?
There is never enough research! Think of personas the same way you think about agile software. Always evolve, iterate and continuously improve.
Persona Cards in all sizes
Chip-sized, used most often in slides with processes
Mid-sized, focused on the challenges of each user
Full detailed cards, linked to Epics, Features and Stories in Product cycles