Do a lot of homework on the different breeders and ask questions. A good breeder will OFA (hip x-ray) their dogs at 2 years old to see if they are or are not fit for breeding. If the dogs are "clean" than their pups are much less likely to ever get hip displasia but it's still not a 100% guarantee.
Every pure bred dog has some quirk that you have to look out for.
Life span wise you can expect 10+ years. The bigger the dog the shorter the life span but the quality of life has a lot to do with that also. My last shepherd before these guys lived 13 years.