Somewhat regularly I'm tempted to try custom IEMs. I have tried various universal ones and they're always terribly uncomfortable, after an hour or so they have to come out so my ears can recover. Even with comply foam tips, sized so they're just tight enough to make a good seal. Drives my ears insane. If custom IEMs fixed that issue for me, it would be worth it.
CIEMs completely solved this problem for me. Like you, I could only stand foam plugs for a short period. Nearly 7 years ago now I got a pair of 4-driver CIEMs from Alclair, and they are still going strong today. I can literally wear them for 8 or more hours at a time without discomfort - this is a godsend for air travel. I put them in before boarding and they stay in until I’m back in the terminal.
