No hatchlings from your own will have what the parents have. I use a long quarantine period but do not add very often often I have rescues and they are quarantined. I don't know how a breeder would add 3 or 4 animals from separate sources it would take one heck of a system to keep everything separate and clean. I suspect few big breeders do a full on quarantine they likely just have a temp space and use that. I know the larger breeders in my area have minimal quarantine as they need to buy and breed asap.

I too do annual fecals for everyone and two checks for quarantine (a single fecal is low accuracy it really takes two separate tests a few weeks apart to be sure. Every bowel movement may not have evidence of parasites) Quarantine animals also get a blood screen as well. If the animal has not come from a breeder I know and one that has not made changes to the collection in more than a year I also do an IBD screen.