It is always good to get a fecal done to check for parasites. If you have an established relationship with your vet he might just let you bring in poop without seeing your chameleon everytime. It will depend on your vet.
When I get a new cham or one that was rescued I usually introduce them to my vet and bring in a new fecal sample. It gives me a baseline of what's there "left over" from whoever had the cham before me, establishes a file with weight, a photo or any other thing I might want recorded, and motivates my vet to read up especially if its a new species. After that, I take in a periodic fecal to detect changes. I find the vet is a bit quicker to help out if they already know the animal and have some basic health info on file. And, as already mentioned, they are a bit quicker to give me a break on tests, getting sample meds like Silvadene, etc.