I waver back and forth. I think once anyone has been through caring for a cavalier with severe MVD or SM, especially one that dies too early because of it, they must have serious second thoughts about the breed as it does absolutely break your heart and is so, so stressful for the people in the household as well. And for other owners with less severe dogs, with any diagnosis of either, with the uncertain roller coaster that follows -- and the expense and the constant watch for worsening symptoms -- that can be very distressing over the years even if the dog doesn't much worsen, because there's always a significant likelihood that they will.
I don't really know whether I'd go for another myself, as I like other breeds too, and like mixes of all sorts.
Going through the final stages of MVD with a dog that should easily have lived several more years as otherwise her health was perfect, and watching her confusion and distress at why she increasingly could do so little, was very difficult. Owners find it becomes so hard to do much day to day -- you don't want to leave them very long, and for months to years, your life ends up being truncated by these often long term endemic illnesses in the breed. I dread knowing my most affected SM dog (which has created 7 years of background worry on its own) also has an advancing heart murmur as well.
I consider myself lucky so far to have had three SM dogs that have not been difficult to manage; especially Leo, as all the indications were that he might be far worse much earlier. It is actually MVD that has been the hardest for me so far. Both MVD and SM have been very expensive to manage. I am also paying now to cover meds for one of my rescues placed with an elderly man nearby -- as I knew she had advanced MVD and didn't want him to cover that cost. It is a lot of money out every month on MVD and SM meds.
This is probably a higher maintenance & costlier breed than many others as they get older too, because of the progressive diseases.
I do think people just naturally, don't think about what their dog will be like when older, when getting that adorably cute cavalier puppy. I agree that there's a point where you wonder about whether it is right to breed a dog that has such a great likelihood of a shortened lifespan due to one or other progressive diseases. Really living to 14-16 should be a norm for a small breed like this.
No definite answer to the question -- I just don't know. Maybe a rescue someday; maybe a puppy someday. I do know this: my partner's dog (GSD) almost never sees the vet, nor did the breed I grew up with. Nor do most of my friends' (with other breeds/mixes) dogs -- can only think of one significant exception. Whereas many of the cavaliers seem to be on something for pain or hearts or epilepsy (also rife in the breed -- was astonished to see a breeder recently claim incidence is
dropping -- researchers like Jacques Penderis see it as endemic in the breed as well!! (this is what he told me last year -- MORE epilepsy than many other conditions, and endemic in the breed). My pal who home-boards small dogs says large numbers of the cavaliers -- always the cavaliers -- come in with meds.
I also do not think I'd now get one for my mom, though she loves them. She is concerned about the health issues and it would be very difficult for her, in every way, to manage MVD or SM if they arose.
All that said many people own and love the breed and muddle through the MVD when they get older as a 'norm' now, and maybe that will increasingly happen with SM as well.
It really shocks me beyond belief that some breeders now argue that we should change our assumption of what is 'normal' in this breed though and accept skull malformations (a malformation that causes distress *is a malformation* bred into the breed, not a new "feature"!!!). It also is very alarming, how readily so many breeders just accept MVD in the breed as well, and do so very little to work to breed it out.