Settings to achieve permanent hair reduction

I’m a 28 year old male, skin type 3. I’ve had 4 or 5 sessions of laser hair removal (laser lightsheer diode) on the back of neck. So far, I’m very satisfied with the results.

I’m just a little worried that hair might regrowth years later. I know that permanent hair reduction cam be achieved if it is done correctly.
***By “permanent,” I mean hair follicle disabled forever, no regrowth after a year or so.

I know that 25 joules is needed to destroy hair follicle. According to my technician, she started with 24 or 25 joules and increased it at each session. The last time I checked, it was 31 or 32 joules.

How can I know for sure if it will achieve permanent hair reduction, or it’s being done correctly? Is there any other settings or anything else that I should ask her about?

Does the success of permanent hair reduction depend on another else besides the settings?