Hey Aussie,
"Guarantee" is a misnomer....it really should be "warranty" as no one can guarantee that a dog will NOT have something develop with its eyes or elbows or hips. What it means to us, is that if something SHOULD develop that the owner of said dog gets a replacement dog or money back or something of that sort. Basically, we can not fix a dog with a problem but we can assure a puppy buyer that we will replace a defective pup with one that is not defective or return the puppy price.
MOST ads do not make dogs have current CERFs. A CERF certificate sometime in the life of the dog is all that is often required.
YES, a pup with RD can grow out of them or they can become less visable. That is why I CERF all my pups before they go to their new homes. That is why people should CERF pups when they are little. MOST people do not, and wait until the dog is an adult.
PRA is not typically a problem in field lines that is more of a show dog thing. However, cataracts are a problem and juvenile cataracts although they usually show up before 18 months of age can wait as late as 5-6 yeas before they are truly visable.
Hope this helps a bit.
Lee