Dumbledore The Senior Citizen?

[D.G.]

No: HPFGUIDX 69461

We've had several pretty broad hints, thus far, that Dumbledore 
is "feeling old," "looking old and tired," that he's been accused 
(falsely, we assume) of "getting old and losing his grip" as Hogwarts 
administrator.  He himself harps on how he, as an old man, forgot 
what it's like to be young, when he apologizes to Harry at the end of 
OoP.

My question:  Dumbledore is about 160, right?  We know that other 
Wizards have lived to be 600 and older.  We can assume, then, that a 
Wizard of 160 is barely even middle-aged, by Wizard standards.  So 
why, then, is Dumbledore portrayed as looking (and, increasingly, 
acting) like an old man?

Is there a Wizard life-expectancy?  Is it the same for all?  Do all 
Wizards age (physically, emotionally, mentally) at something 
approximating the same rate?  After all, Harry and his fellow 
students [as well as slightly older Wizards, like the older Weasley 
boys] all seem to be about as old/mature in Wizard years as they 
would be in Muggle years.

How long does this continue, before the Wizardly aging process (of 
lack of it) kicks in?  This is especially pertinent when we start 
thinking about the age at which various folks' parents or ancestors 
might have married, had children, and so on.

D.G. ("JazzmanChgo")

P.S:  is it significant that we've thus far seen no evidence of any 
of the boys' voices changing  -- or, for that matter, any of the boys 
OR girls developing adult-like physical attributes such as facial 
hair, breasts, etc.?   Remember what Snape told Harry:  "Time and 
space are important in magic!"  (Can't find the quote now, but I 
definitely remember it -- another of those tossed-off lines that I 
think will have major significance later on)