As far as I know, Mr Case did acknowledge that maintenance sessions are required couple times a week after the initial month in order to keep tinnitus from coming back.
So the effect is definitely temporary.
But here is the thing:
If this particular sound is able to keep tinnitus at bay for so many people, why all the hostility on your part?
It could well be, that this sound really is superior at suppressing tinnitus from all the other sounds out there.
Instead of being happy that some people have indeed found Tinnitus Mix to be helping them better than any other forms of available therapy they tried to date (most of it not free), you chose to attack Mr Case instead.
This is what I have problem with.
Speaking for myself, if I could achieve silence, while having to do some kind of a maintenance sessions here and there, I would consider myself cured.
Bimodal stimulation will also very likely be a form of suppression with maintenance sessions required, yet people are quite excited about it.
So if the final effect is essentially the same, why embrace one and attack the other for not being "lasting" (as you put it).