OoP - Wizard's Ages

[Claire]

No: HPFGUIDX 66939

I haven't seen this posted yet (but haven't read them all).  The OWL 
examiner, Professor Marchbanks, says she examined Dumbledore 
personally in his Transfiguration and Charms NEWTs.  Since DD is 
around 150 years old, that would make Marchbanks considerably older, 
and without the apparent aid of the PS/SS!

Actually, I suppose I'm just wondering why some wizards/witches have 
great longevity.  Or is this normal in the WW and those who die at, 
say, 80 or so don't die of natural causes?

Just a random thought.

Claire