I haven’t read nearly enough by Jack Vance. The omnibus of his Dying Earth stories is in my “to read” pile.
But it may take a while to get to it, since I’ve belatedly discovered Gene Wolfe. (Thanks to SDMB.) Apparently the Dying Earth influenced Wolfe’s Book of the New Sun.
Yes. My take on Narnian time is that it’s entirely disjoint from Earthly. It’s not that 1 Terran second = 1 Narnian month, or anything so linear; the calendars of the two worlds are simply independent of one another. It’s only through the grace of Aslan that the adventures of the Pevensies & their friends occur later and later in Narnian time as the english calendar advances. Consider the ancestors of the Telmarines; they were 19th century pirates, but they arrive in Narnia long after the Pevensies adventures began.
As to your question, I think the 3 visits in LWW all have to begin within a fairly brief period, as Narnia is inthe 100th year of its unending winter in all 3 cases. But I doubt anyone but the Great Lion could be more precise.
Yep - the book is quite a bit clearer about the time scale (weeks), and the movie editing isn’t quite as clear.
But I liked the approach. As time goes by, the character hears more words correctly, until he can respond to a (sexually based) insult (directed at the apparently uncomprehending stranger) with a “your mother” - provoking a reaction as detailed above.