I've wondered the same thing. I had 12 years between flare up number 1 and 2. then I had 16 years between number 2 and number 3. I have wondered why all those years I didn't have problems if I had the abnormalities all along. (I had the procedure done in Bulgaria)
Another strange thing, with my second flare up I had right ear pulsatile tinnitus and this time it is in the left ear, which if I understand correctly is due to pressure or compression on the opposite side of the neck.
So I wonder, if my veins opened and closed on their own over the years.
By doppler testing, it shows that I have re-stenosed.