The pediatrician I take my daughter to has a free nurse line, I call in any time I think I need to bring my daughter in due to sickness. Talking with the nurse she asks how long the cold/cough/whatever has been present and then either tells us to wait to see if it goes away in a day or two if not come in or if she has had the symptoms for a few days to come in. So far I have never gone in without recieving a treatment of some sort (medicine or further appiontment set up to see a specialist). To me it is my childs health I will do what needs to be done and pay for that treatment if need be... my doc office actaully does not charge if we come back within a week with the same thing that has gotten worse BUT they only do that if you are not always bring your kid in at the first sign of a cold/cough/flu (have to wait 2-3 days if getting worse or high fever, over 101, is not going away after 36 hours).
As a mom you have to do what you think is best, I tend to not take my daughter in until she has had a cough for a few days because I know the doctor will not give anything unless it has been around for a few days or sounds a certian way. If your child does have an issue of always getting something then do stand your ground, maybe find a diffrent doc that work better for you/child, and it is hard to predict how a sickness is going to go sure the docs know a lot but they do not want to medicate a child for no reason that only weakens how will the medicine will work the next time they really need it. A good doctor will not treat unless there is something to treat, a cold, cough, flu usually has to be dealt with at home, just because they get an ear infection for it does not mean if treated before means that it would have not happened.