I can possibly guess the sire referred to on here - if it's the one I'm thinking of he has sired 100 litters to date

There is no limit on the use of stud dogs - it may be something the KC considers in the future but at the moment, any dog can be used as often as the owner allows & if it's a well-known stud dog who has produced good progeny, then people will continue to use him. Some stud dog owners are very selective and others are not (or don't like to say no to anyone

). As long as stud dogs have the magic "Clear" for both DNA tests, lots of breeders don't see any problem in using them over and over again no matter how short-sighted that might be (it's as if the two conditions we have DNA tests for are all that matters).