threat levels, concealment....
I'd say use common sense & good judgement.
I live in a metro area with a lot of tourists & a daytime population of approx 1,000,000 people.
When I had my concealed license; 2002-2007, I packed a firearm about 25-30% of the time. Now, I also toted my loaded .38spl revolver or 9x19mm pistol in a street legal, secured gun case in my vehicle. When I drove around, I was armed 75-90% of the time.
While I agree that most violent crime involves criminals(both subject & victim) and has high risk elements(crime, alcohol, illegal drugs, etc) you can't assume you(as a upstanding, citizen with a valid carry license) won't be involved in a lethal force incident. Being armed means being alert to danger too!
A few years ago, a veteran police officer in my city was killed in a off duty robbery incident at a ATM. The armed robbers shot the armed, off duty cop and took off.