My best friend has 3 PONS! They're a rare breed, so I was surprised to see a thread about them!
Her dogs are great, and I've learned quite a bit about the breed in the 5-6 years I've known my friend. Hers are aged 16, 14, and 8. (I'm posting a pic of the youngest one, Ruby.) Obviously, they can have a very long lifespan if raised properly. They require tons of exercise (but my friend likes to run, so she just takes them with her...) And they eat a TON!!! The youngest is terrible about food -- she once stole an entire brick of gruyere cheese off the kitchen island, right in front of everyone.
They're extremely intelligent dogs, and very affectionate. However, they require regular grooming (at least 1-2 times a month), or they get really dirty and kinda stinky. Her 3 are good with each other, since they've grown up together. (The 14yo dog is actually the 8yo dog's mother.) She also has a cat, though, and the dogs hate it!
As far as any illnesses they're prone to, I know that the oldest has bad arthritis in her hips, and the other two have thyroid problems. (Ruby, the youngest, is actually about 10 lbs overweight as a result.) So far, they've had a relatively easy time managing the dogs' health problems, which are actually pretty minimal considering their age.
Anyhow, PM me if you want more info or some links. My friend's mom is actually a former breeder, so I can get some more info from her if you're seriously thinking about getting a PON.
And... here's Ru!