It's going to be almost impossible for someone to give you the exact answer to your question. How often you use the brakes in moderate traffic compared to how often I use the brakes in the same situation may be very different. So, what I would suggest is that you figure out what is normal for your rig, the way you drive. You can do this by checking the temps with your no contact thermometer every hour or so while driving. It will help to write down the temps on a sheet of paper and a brief description of road conditions each time. I.E. Stop & go, City, level freeway, etc. Pretty soon you will be able to see what is normal for your rig, the way you drive.
I shoot the temps on my front tires where the tread meets the sidewall, the aluminum wheel between two lug nuts, and the front disc rotor, which I can see thru a hole in the wheel. I shoot the rear outer dual tire in the same place as the fronts, and between two lug nuts. The rear inner dual tire same as the others and the tag axle tire and lug nuts as described before.
Here's what I'm looking for. On the tires low pressure will create heat. (I do have pressure and temp monitoring on each tire but I monitor heat with the thermo anyway) The wheel between the lug nuts will heat up if an axle bearing is going bad and/or the brakes are hanging up. The front rotor will be hotter than normal if a brake is hanging up, and/or bearing is going bad. Comparing side to side will sometimes vary a few degrees but not drastically, if you're driving in hot sun on one side.
The accuracy of all this depends on nothing being wrong with your rig now, when you're checking and making your initial measurements. But where else could you start? Pretty soon you will be able to just walk around shooting readings and immediately know if something is hotter than it should be on your rig.