Well, after the CH they have recently created another title, that of “Grand CH”. I’m not sure exactly the requirements other than continuing to amass points by beating other dogs. Some people do retire the dog after they have achieved the title, but some don’t. Of the ones that do, it is often because they have another dog they want to put the time/money into. But continuing to be out on the show circuit a) gives the owner the fun of wins/showing, especially if they don’t have another dog ready to campaign and b) provides good marketing, especially in the case of a stud dog - the more people that seem him out there winning, the more that will be interested in using him, or in the case of a bitch, the more that might be clamoring for her puppies.