There are a few facts that need be considered before embracing any type of explanations.
1.The jugular vein is located inside a membranous sheet and packed together with other important structures, i.e. the carotid artery, the vagus nerve and its accessory branch. The higher we go (towards the base of the skull), the more these structures are tightly packed. The tunnell is surrounded by the neck muscles and is in contact with the sympathetic cervical nerves.
It is therefore possibile that a rigid structure, like a stent, placed high up into the jugular vein, may interfere with the function of adjacent structures.
2. Sweating is regulated by the sympathetic nervous system
3. Stimulation of the vagus nerve may cause nausea and vomiting
4. Irritation of the accessory branch may cause pain and spasms in the shoulder
In order to try to reply to your other questions I must clarify that there is no reported evidence regarding the fate of stents in the jugular veins: we simply do not know because the experience is being built up, thanks to the bravery of many patients who accepted to be guinea pigs for the benefit of others.
If stents stay open for ever we will open the champagne, if they do not their removal or re-opening is not going to be a walk in the park.
In addition, we cannot extrapolate the behaviour of stents in other anatomical locations and apply it to the jugular stents: this is a new location never used before.
Based on the evidence provided so far, my personal opinion is that I would prefer to undergo a balloon dilatation every six months rather that having a stent. I understand that Dr Dake experience is different from Zamboni's one, in that he found the stenosis high up towards the skull and, according to his reports, balloon dilatation was not effective: apparently stents offered the only solution.
I hope my answer to your questions is satisfactory.