With my dogs there are two reasons we can keep tightening up and not get hurt by turning out inbred bums. One is selectivity, always trying to go to the higher end of the line. Second is that we keep breeding individuals from two sides of the line together to essentially refresh the original cross. You can do this kind of "cross" in a tightly inbred family over and over and over. Your average dummy looks at a pedigree like that as "inbred", and often avoids it because of a perception that the dog is bred "too tightly", giving no credit to the breeder's understanding of the genetics at hand. This is because too many dumb breeders in history have stacked pedigrees with little regard for selection and turned out litters of nothing dogs that only had some fancy names in the pedigree.