As for wear and reuse. That becomes your pattern. My wife is a nurse, teaches it, and is hyperattentive about having things clean and not contaminated. Funny she doesn't bat an eye about my reuse. Typically I use mine about two weeks on the daily commute. They usually aren't grimy at that point but starting to look unfresh. When I get off the bike, I lay them on the inner faring tray next to the instruments. Grab them first when gearing back up.
The helmet is sitting on the gloves on the top of the handle bar mounts. So jacket goes on, then ear plugs, then helmet then gloves.
Now as I say this, I also realize from experiences across time, different peoples ears had different wax and oils.
Find a pattern that works for you, and wear them.