Occasionally I see a new answer pop up on a REALLY old question (like 8+ years). I have done this a couple times myself, but mostly on accident when I didn't realize how old it was. I mostly try to avoid it because it just feels...weird. But I have also seen some old questions that I feel like I could contribute something to.
My gut tells me that there is absolutely nothing inherently wrong with doing this and my discomfort is entirely self imposed. But before I "get over it" and go digging around for old questions to answer, I want some clarification on what, exactly, the general consensus on this is.
A. It is highly encouraged, but underused
B. It is good thing, but not all that important
C. Nobody really cares
D. It is acceptable, but only occasionally
E. It is to be used with discretion, only if there is a really good reason for it (and what a good reason might be)