What, if any, conditioning do you do? At what age do you begin a "structured" conditioning program?I don't know if these types of questions are helpful to anyone else, but I learned from the thread about show grooming and really appreciate everyone's input.

I don't have a regular conditioning program, but I do swim my dogs regularly at a nearby lake. Throughout the Spring and Summer, I work them in the field, which keeps them fit and conditioned for the show ring.

I do daily off leash 'walks' - I walk, they run :-) in the various parks/woods in my area. One park I go to is all hills and valleys - great conditioning for all of us. The younger pups I just let play in the dog yard and take them on leash walks. Swimming for everyone weather permitting.

Swimming is SO good. Dogs of all ages ( not tiny pups, of course) can swim to get or stay in great condition. If you are lucky there may be an indoor dog pool near you. So that even in cold climates you can keep up the fun-fitness year round.
You can even join in events for competition involving swimming.
caninewatersports.com - awesome resource for "all things water -dog"

Structured running/retrieving and swimming/retrieving program beginning gradually at 2 years old.