One thing to mention...a lot of vet's won't do just a fecal exam on an animal without doing an "initial" exam to set up a Vet/Client/Patient relationship. One of the main reasons for this is because they are not supposed to prescribe medicine without having a relationship with the patient. If your snake has intestinal parasites, they may not give you the medicine without seeing her first.
Typically after the first exam and fecal, you should not have to take the snake back unless she is sick. You should also talk to the vet and let him know that since reptiles do not get sick very often (with proper husbandry, that is), and that in the future you would like to just drop off a yearly fecal. Basically, let him know your expectations up front.
By taking your little one to a reptile vet this time, you also can find out how much he knows. This is good information for you because in the case of an emergency, you do not want to be hunting around for a knowledgable reptile vet.