I never said you can't fly/run/exercise/drink/listen to loud music (concerts). What I said is, These activities may cause you to have a poor day afterward. Most are more sensitive to alcohol. They may get drunk easier or have a hangover that is more problematic. I did not say you cannot fly. I fly in airline cabins. But, private pilots flying in unpressurized cabins at high altitude for extended periods may be putting their safety at risk. Flying as a passenger is not a risk.

Exercise that cause high peaks in pulse and BP may cause headaches more easily that prior.

If you choose to go to a loud concert and have a bad day after, take it slow and you should return to normal soon. I just would not plan a loud concert the day before a critical task at work or elsewhere.

If you find from experience that you can push the limits, good for you. Most people do not connect their prior concussion to later bad days. Instead, they might load up on caffeine thinking they are just tired.

btw, If you like loud music, spend a day in a retirement community and observe the frustration people have when they struggle to hear. I have a 10% loss in the high frequencies due to noise.

It's not like these activities will cause PCS to come roaring back. Just that they may cause one to have a slow/bed day. As you age, you will find that many body systems have less tolerance for stress. This is true for people who never had a head injury. It's just more so for us.