The only thing that will tell the truth is time. When people use it after a week, then go back to using regular vaporizers, AT A TEMPERATURE OF 385f, AND UP, they would be able to differentiate between the two. Chances are regular vaporizer won't be strong enough, unless they take their time, and let the vapor build up in their system which is how cannabis or any food works when ingested in a healthy manor. The reason it may not be strong enough is because they are experiencing adrenaline fatigue, which lowers cerebral blood flow, and in turn will raise their tolerance. If it does what it says, and allow more cannabinoids into the system without the adrenaline rush that I state, they should still be able to be satisfied with a thin mist a regular vaporizer can provide being that it's approximately the same amount of cannabinoids going into the system.
Also, if they feel they have less energy to do active things after the first week, then they have accumulated a lot of cbn in their system, and it made them lethargic. The only way to tell is if they try to do a nice run. If they are using a regular vaporizer correctly they should not be too tired to run, but if they have a build up of cbn, and have low adrenaline, they just want a nice jog or just a walk due to not having the energy to get going from excess cbn, and adrenaline fatigue.