I would definately get a fecal done on every new snake you get regardless of the breeder. No matter how careful and responsible the breeder is, no one is immune from parasites. I bet if you ask these "responsible breeders" if they themselves recommend you add these animals directly to your colony, I am sure even they would say to quarantine your new snakes no matter what. I would also quarantine for at least six months, unfortunatly sometimes things can be harbored for even longer than that.
If you haven't already, I strongly suggest you read Cowboyway's post on crypto. If you consider how easily it can infect water, and how difficult it is to get rid of it (bleach does not even work), it is very scary. So if you "commune wash" all your water bowls/deli cups in bleach, transmission can still be very possible. I myself am leaning towards disposable water containers after reading up on all this.
I just recently got around to testing some animals I aquired in the last six months. Even though these animals have been totally symptom free for the past six months, some worms and bacteria were found. It is very worrysome to think what would have happened if I relied on quarantine and symptoms alone. Now I have them tested right from the start and have them tested a few times before I even consider bringing them in the same room as my breeders.
I pay about $13 per fecal to me the cost of 3 fecals ($39) is nothing compared to the worth of my collection, or even one of my breeders. Heck, that is how much we are all willing to pay for shipping. I guess it all comes down to how much you like to gamble.