Cavaliers are wonderful companions and great family dogs but they are very health compromised.
I appeared in the PDE documentary. I can assure you that it was not overstated.
If you buy a cavalier you are taking a chance that you will end up with a dog that has a heart that ages earlier than other breeds. Cavaliers with early heart murmurs can go on without any problems until really old. Others can die breathless and unable to exercise at seven years old.
You also take a chance that your cavalier may develop Syringomyelia at some time. Some cavaliers have shown painful symptoms that could not be controlled while still puppies, some have died when in their teens without showing any obvious symptoms.
I have had quite a few SM dogs and watching them and wondering just how much discomfort they are in is not pleasant. There are drugs that can control SM pain but getting the combination & the dose correct for the individual dogs, the constant need to tweak & increase the dose, can be a nightmare.
If you buy a cavalier you need to give yourself the best chance of a healthier puppy by buying from a truly responsible breeder. One that eye tests (cataracts are showing up again in cavaliers) heart checks and MRI scans when the cavalier is over 2.5 years old, not someone who tests when the parent(s) are really too young.
You need to be aware it is not what breeders say that proves they are responsible, it is being open & honest and willing to show all health certificates.
As a sensible buyer you need to know how to read those certificates. There is plenty of information about puppy buying on this site.
Cavaliers......Tommy Tuppence 2000-2012 and a half share of Faith.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.