I raise LGD's full time, own 9 imported Spanish Mastiffs, four imported Pyrenean Mastiffs, and an assortment of Great Pyrenees, Anatolian/Maremma crosses, a Kangal, a Kangal cross, etc. on my ranch where they all guard my stock, my ranch, and me. I guess I'm kind of hardcore pro working homes only, the only exception I have ever made was the Pyrenean Mastiff, which has a less complex personality than some LGD's, is very stable, loving with its owner, non-aggressive towards strangers yet a very adept guard, and fabulous with livestock. I really balk at selling my LGDs to pet homes in towns. They need the room to run and exercise, they need a job, they need to guard something, preferably livestock. Although I know there are CO and CAO's kept as pets, well, a lot would depend on your dog experience as already discussed above. As for nerves, I don't own a 'nervous' LGD in my pack, maybe because they were ranch raised, in a pack, I don't know, but none of my dogs are ever temperament tested, nor are my pups. They are pack raised, they learn pack dynamics from day one, that kind of 'nervousness' does not crop up ever, there are dogs here at my place who are more suspicious of strangers than others, but overall, stable, trustworthy, calm but highly vigilant and fierce protectors. So I don't exactly agree with the weak nerves statement in 'all' guardian breeds. As for temperament testing and grading pups, I know of no big sheep or cattle or goat outfits raising their own LGDs who bother with that. Out here, papers are smirked at, no one really cares, what they care about is working instinct, stamina, and the dog's bond with the stock. All the rest is window dressing to most ranchers I have worked with or sold pups to.