As far as I know, I don't have SFN, but I do have an experience with spinal cord stimulators. I had the Medtronics SCS trial and implant back in 2018. This was a result of lower back and buttocks pain from a ski fall. The device, along with pain meds, helped reduce my pain from about a seven down to about a two. It lasted for about two and a half years and then just stopped working. The thought was that some of the electrodes on the paddle lead burned out. I had everything removed a year and a half ago. A new stimulator trial was attempted but there was too much scar tissue to get the trial lead in place.
As you research, you'll find plenty of pros and cons. I have seen a number of positive reviews and quite a few negative reviews. Be advised...having a great trial is no guarantee that the permanent implant will give relief. I wish you well/