Yes you can get scared by people coming up behind you. With the ER-4 I also sometimes here details in songs that a mistake as coming from my room and that scares me. I didn't think my etys changed with burn in, I am not skeptical of burn in though, I think the senns changed a lot.
The itching could be aggravated by your ears not being clean enough, or being too dry, alcohol is very drying and I recommend against using that to clean your ears. I never itched with the tri flanges, I use foamies now and sometimes I get a little short lived itch, but this is rare and only when my ears are less clean. So as for itching, try improving your ear hygiene if you think this is suspect. If you have a lot of wax built up you can get a removal kit with drops and a bulb syringe at any drug store, you just need the drops but the bulb syringe is used to flush your ears out. I just use soap to clean the outside of my ear when I shower and let the shower water run it in my ears, that keeps mine pretty clean. If your ears are clean you might try some of the lubricants sold to hearing aid users. Some people just seem to be sensitive to the pvc material the flanges are made out of, but this seems very rare.
It seems that average filter life is around 6 months, I haven't changed mine yet in the 4 months I have had them.