My tires are at the default pressure from the day the car was delivered (a little over a year). Except for a four month "break" (car in shop following an accident), I drive it almost everyday and have accumulated over 6000 miles. I drive mostly on congested roads and suburban streets. I occasionally "put the pedal to the metal", mostly on highway on ramps. I do not race and rarely exceed 65MPH.
My rear tires still have about half of their thread left. By half, I mean the amount left above the wear bars is equal to the bars' own thickness. I will probably have them replaced at my next annual service, in December. The front ones are barely used. I guess they will last 50% to 100% longer than the rear.
I think driving on twisty roads has a significant impact on tire wear (added side stresses). The road surface on which you drive also impacts wear: a more abrasive surface such a rough concrete will claim more rubber than a softer asphalt. Of course, pot holes and other sharp impacts can't be good either!