I've been using these about a year now. I travel a lot and these have been the best I've found. I keep them in my ears even when not listening to music. They are a little pricey but worth it.
HiHo,
while reading your post, I remember how hard it was to find some headphones that are comftable enough to wear them at least 12h per day.
For me, it was very important to get as much noise cancelling as possible and have a very high quality sound.
After testing many, this is the one I bought (and the only one I even considered to keep) : https://www.amazon.com/Shure-SE215-CL-Isolating-Earphones-MicroDriver/dp/B004PO10E2/ref=sr_1_2?s=electronics&ie=UTF8&qid=1513568028&sr=1-2&keywords=sure+in+ear+monitors
What I liked very much are the earbuds. They are made of foam that will expand in the ear canal. You can buy it as spare part and maybe it will be a "small upgrade" for someone.
Actually, the best in-ear buds I've ever used for sound isolation are Shure earbuds. My husband and I play in a hard rock band, and we use these for in ear monitors in practice and on stage. When I have them on, even if there's nothing coming through, I can barely hear anything. They are not active noise cancelling, but they are excellent at isolating sound and they are a little cheaper. Just something to try out as an alternative. :)
Edit: I also get a lot of mileage out of my ~$15 JVC marshmallow buds for office settings. They're really not bad, sound quality wise, for the price. However, they're only useful when music is on. They do muffle external sounds fairly well, but not completely.