I just had a follow-up appointment with the doctor who did my first procedure. He indicated elastic recoil was normal and that repeat procedures could be the norm for many people. He said it would take some time to find out what the normal rate of restenosis would be for people with MS, but repeat procedures are standard for many vascular conditions, each of which has its own unique profile for restenosis because different anatomical locations produce different venous conditions. He thought it was probably unrealistic for people to think that ONE procedure would address their entire lifetime of MS issues.
It was actually very positive. Far from thinking that a return of symptoms meant that there was in any way a failure, he thought that could be positive, because it could indicate that there was a cause-effect relationship -- and a repeat procedure could make a difference, with possibly scheduled yearly maintenance, and potentially an overall better safety profile than something like a monthly infusion, with higher risks of PML, cancer, infection, liver damage, etc.
Mind you, I should make it clear that this is *me* blabbing and interpreting here, so any errors are mine.

But yes, elastic recoil apears to be a big issue, and addressing it will really help. I think this is what I've experienced.