Longevity isnt really something you could definately breed towards though.
Many things factor in when we are thinking of our pets life spans (even our own)
Its like nature vs nurture, even if breeders did select from lineage that had long life spans and someone purchased a pup who potentially had a longer life span than most, too many environmental factors could come in to play to reduce that span.
Diet, excercise, general housekeeping, smoking or not ect.
Everything we do to our pets in some way affects them.
Kita for example is one of the few dogs alive out of her litter right now.
One has passed from bone cancer, one passed quite young due to obesitiy I'm sure and one of her sisters is not doing well right now, she has bad elbows, hips, full of lumps and can't keep weight on.
I know her one sister was always encouraged to be "larger" because her owner figured that since she was part Rottie she needed to look it. But did not take into effect that she was also part Boxer and perhaps just wasn't supposed to.
Kita you would never know is 8 years old other than her slightly greying muzzle. She runs like a pup and has energy to the max.
She also was the only one fed organic raw for half of her life and kept very fit and trim. Also has not had vaccinations for the past 4 or 5 years as they would have been unnecissary.
I do not doubt she will be here atleast another 2 years if not more.
As for Karma, her grandmother was 19 when she passed however her mother passed at 8 ( unusually young for a TM) but she had complications after her spay.
On the topic of the study of the Rotties left intact longer. I completely agree that the hormones produced by intact animals are benificial for their over all health but do not see it as a reason to not spay or neuter.
Kita was also spayed later on in life where as the others were altered at 6 months.
I almost regret gelding my horse last fall, I would much prefer him not hormone driven for training reasons however his development has slowed quite drastically since the gelding. Not sure if its directly related or not.
back on my origional point though... it would be almost impossible to ensure a breed of dog would have a long lifespan unless the breed also came with an instruction manual of do's and don'ts. No one would follow what I do for my dogs to the extent we do it around here, but it has been working great for us
