As Perm. Secretary for the Alumnae Chapter, I can probably vouch that the address that IHQ has is the most current one that THEY have which means if the sister and/or collegiate/alumnae chapter hasn't informed IHQ that the sister has moved or even died, IHQ has no idea.
The complete list of Gamma Taus that I got last spring had addresses of sisters when we were initiated a couple of decades ago.
I would say that the same thing probably holds true for the Chapter's collegiate info. All I can say is that Audra Hansen & her staff in Member Services have been terrifc in helping me straighten out 30 years worth of names, not to say that we both have correct addresses. I just gave her what I thought were correct or left them as IHQ had them.