JK said in an interview from 2000: "Dumbledore is a hundred and fifty, and Professor McGonagall is a sprightly seventy. Wizards have a much longer life expectancy than Muggles." Later she changed Dumbledore's life dates to 1881-1996 (here: Wizard of the Month)
Canon seems to imply that the stronger a witch or wizard is magically, the longer her or his life-expectancy may be. I don't have actual proof or quotes for this, but it was always my impression.
The Black family is an interesting case, because despite being one of the oldest magical families in Britain, the Blacks generally don't have unusually long life-spans, see The Black Family tree. Certainly nobody of that family lived as long as Dumbledore who was 116 years old when he died (not a natural death, either). Sometimes, in fanfic, there is this notion that "purebloods" live longer than "half-bloods". The Black Family Tree clearly says that this is not true. (Obviously, really, because there is no difference, biologically and magically, between "purebloods" and "half-bloods".)
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Canon seems to imply that the stronger a witch or wizard is magically, the longer her or his life-expectancy may be. I don't have actual proof or quotes for this, but it was always my impression.
The Black family is an interesting case, because despite being one of the oldest magical families in Britain, the Blacks generally don't have unusually long life-spans, see The Black Family tree. Certainly nobody of that family lived as long as Dumbledore who was 116 years old when he died (not a natural death, either). Sometimes, in fanfic, there is this notion that "purebloods" live longer than "half-bloods". The Black Family Tree clearly says that this is not true. (Obviously, really, because there is no difference, biologically and magically, between "purebloods" and "half-bloods".)