Future Nostalgia II

Maybe alternative histories date less quickly than futuristic sf? Of course, if the author's "present" interacts with the alternative history, as it does in HG Wells' Men Like Gods, then that "present" dates just as much as the author's "future" does. However, a narrative that merely presents an alternative version of the English Civil War or of World War II is already set not only pastward from the present but also sideways from the known past - go back to the seventeenth or the twentieth century, then turn right! - so it is not likely to date very quickly.

A historical novel set in the twentieth century might present fictionalized versions of, e.g., Queen Elizabeth or Tony Blair. The novel dates if its view of those historical figures comes to be seen as outmoded. An alternative history novel can give us those same characters but in a changed situation so there is less danger of outmodedness. Previously undisclosed documents can shed new light on how the Queen or the Prime Minister did respond, e.g., to the death of Diana but how they would have responded to the Change will remain forever a matter of conjecture. None of us can know for sure how we would have responded to such an event.

So maybe the alternative histories remain immune to the passage of time and will always be as fresh when read as they were when written?