My original 123 Brake Rotors went over 500,000 highway miles before replacing the fronts, the rear ones are original. The fronts were okay, but getting thin and replaced out of convenience when getting an entire front end from low mileage parts car. I never experienced a warped rotor on this car.
I have never used a "torque wrench", however, I always hand tighten with the factory lug wrench in a five cornered star pattern. I put the same weight on them and torque them as evenly as I can with the lug wrench. The times when I have used a tire store where I don't put the wheels on myself, I actually loosen and "retorque" the wheels with my lug wrench on the parking lot before driving away and heating the rotors.
This technique has worked well for me. I own a very nice torque wrench, but the above has proven to much more convenient, and I think has also proved adequate.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in