At a median household income of $176,602, Cos Cob isn't a place where people are stretching to keep an old door running past its useful life - most owners here replace rather than nurse a door along for years once it's clearly done. That changes the kind of call we get: less "make this limp through another winter" and more "what's actually wrong and what do I do about it."
The houses themselves, centered around that 1959 build year, tend to have single-car or two-car attached garages built to the standards of the era - narrower openings than a lot of newer construction, and door heights that don't always match what's sold off the shelf today as a standard size. That's not a problem, it just means measuring carefully before ordering a replacement door rather than assuming anything is one-size-fits-all.
We don't have a count of exactly how many of those original doors are still in service versus already replaced - that's not something we track by neighborhood - but the age of the housing stock alone tells you a meaningful share of this area's doors are nearing or past the point where repair stops making financial sense.