Quite a wide variation there, and it's also important to remember that there is no absolutely 'average' Rottweiler, there is room for error on both ends of that spectrum and every dog is different.
Many rotties live for considerably longer, many others die earlier. Every dog is an individual and has their own health challenges and environment, so there's no one-size-fits-all figure.
It could be worse (many giant dog breeds have even less longevity, such as the Irish Wolfhound who only has an average lifespan of between 6 and 8 years, the same for the Great Dane) but it's definitely not great
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