Here's my experience, having lived with it (undiagnosed) for at least 25 years. My problems began in the 1980s, when I was doing a fair number of triathlons. Right before Kona one year, I started getting odd left leg pains. I raced well that year, but the next couple of years were increasingly frustrating and I eventually gave up triathlons. I was still able to swim, could do some cycling, but couldn't run any more. Over the years, my leg became increasingly painful and my cycling increasingly frustrating. My swimming held up because I learned a two beat kick and then a no beat kick. :) Eventually I also started having right leg problems, then a dvt/pe which really seemed to increase the pain and dysfunction. Bilateral iliac artery endofibrosis was diagnosed quite accidentally in 2011. I had bypass surgery on both sides and am loving life. Too bad I lost 25 years, but at least they found it and it could be corrected. My n=1 experience, though, is that it was progressive; there was no improvement with decreased activity/intensity. Maybe it does improve sometimes, I have no idea. It certainly didn't for me. I can say that I didn't realize how much of an impact it had in all areas of my life until I had it corrected.
None of which is meant to minimize the dangers of the corrective surgery or imply that everyone has positive outcomes, nor am I suggesting that the only option is to go ahead with the surgery. Obviously you have to do your own risk/benefit analysis. The surgery worked for me, but I know someone who did not have a good outcome and it is undoubtedly a risky surgery (there was a pro cyclist who died post-surgery, as I'm sure you have seen). Whatever you decide, I can't emphasize enough how important it is to see a vascular surgeon who is familiar with this in athletes. The first one I saw was not and it was not a good experience. If you would like to talk privately about it, feel free to message me. Good luck with whatever you decide to do.
None of which is meant to minimize the dangers of the corrective surgery or imply that everyone has positive outcomes, nor am I suggesting that the only option is to go ahead with the surgery. Obviously you have to do your own risk/benefit analysis. The surgery worked for me, but I know someone who did not have a good outcome and it is undoubtedly a risky surgery (there was a pro cyclist who died post-surgery, as I'm sure you have seen). Whatever you decide, I can't emphasize enough how important it is to see a vascular surgeon who is familiar with this in athletes. The first one I saw was not and it was not a good experience. If you would like to talk privately about it, feel free to message me. Good luck with whatever you decide to do.