I think it depends very much upon the procedure used to implant the device, to make it work like it did during the trial!
When my device was implanted, they woke me up from my anesthesia, to check on the proper electrode positioning. They moved the electrodes until i could confirm that I was free of pain. Once this was established, anesthesia was reapplied and the final surgical procedure was finished.
A week later, I started to work with the technician to establish the optimal adjustment of the handheld control unit.
This device allowed me to become a normal member of society again instead of a person who could hardly move because of all the pain.