I've worn masks for extended periods day after day when working in cleanrooms. You get used to it quickly and stop really noticing. The thing you pay attention to in that environment is where your hands are, what they've touched, and do you need to change gloves. The mask stops being noticeable pretty quickly.
Things that make a mask more comfortable:
1) fastens behind head instead of over ears. It gives you more control over how it presses. I usually use tie behind rather than elastic. It's also secure if you need to pull it off for TSA - I just pull the top loop over my head or down below my ears, and leave the lower loop tied.
2) flat metal strip over your nose. it helps seal around your nose and also helps keep water vapor from coming up and fogging your glasses if you wear them.
3) 3D geometry. Paper (mostly really blown poly) masks are structured in ways that keep them from sucking into your mouth. Fabric masks tend to just pull over your mouth and feel like they're sucking in. I have a bunch of duckbill style that I like, as well as KN95, and some cheap flat pleated masks. The duckbill are my preferred mask because they tie behind (KN95 are earloop) and have a lot of space. There are also silicone mask brackets you can get to keep masks from sucking in, but I've never used one for more than an hour.