Heh. You know, I remember reading Elfie's great feat of leading two patrols as a child, and not understanding but being convinced that the failing was somehow mine.
On the 'guide book' effect: I'd previously put this down simply to her being personally familiar with Pertisau, Herefordshire etc, whereas it seems highly unlikely she had ever visited Switzerland - but increasingly I think it's probably more about her declining writing power (or effort?): I think this c/o the island books, which are not my personal favourites but are remarkably evocative of their location in spite of it quite probably being fictional (I know there is a line of argument that Carnbach is Tenby but there seems plenty of reason to dispute this). And the gap between the brilliantly-captured characters in the first half(ish) of the series and the weaker, transient characters of the latter suggests the same. Her earlier characters are bloody glorious, some of them.
Likewise I can tolerate much more rehashing earlier in the series, and I think it has to be simply that it's better done. I think it's Bob Dixon who complains that all the girls are able to do is fall repeatedly down holes, and he's not entirely without a point: but still, Jo falling down a hole in Camp feels entirely reasonable to me, and when Corney falls into the belly of the mountain (;)) in the very next book I don't find myself going "oh, here we go again". I'm still perfectly happy to accept Peggy Burnett falling down a hole in Shocks. I don't really roll my eyes at Joey being the heroic rescuer in Princess, Rivals, and, er, which is the one where Grizel goes off up the Tiernjoch? Because I think all of these are well-written and although Joey looms a bit larger than life, I buy into them as pieces of fiction.
I obviously can't comment on the accuracy of the later books as depictions of the 1950s/1960s, though am v interested to read thoughts on this. It makes sense to me - increasingly I get a sense of an ageing woman who is decidedly unimpressed by Modern Life - as I suppose is frequent but by no means 'the normal'. I wonder if EBD thought of her books as being set in the time she was writing, at that point? (Am thinking in terms of the 'dating' I know some Chaletians prefer, whereby the triplets are taken to be born in November 1939 and so all books' dates are taken to be in accordance with that - so when they're leaving in Prefects, pub.1970, it's supposed to be 'set' c.1958 - I mostly feel sceptical about this kind of dating but it's an interesting one, particularly as the somewhat artificial environment of the Platz gave EBD a lot of licence to fudge her setting.)
Later on I think she's averaging two books or even three a year, isn't she? I'm too lazy to look it up right now. I do wonder what that was like, shifting from combining teaching and writing to writing full-time - I suppose I'm partly intrigued because for me, that's the exact point at which the series nose-dives (Three Go) : the liberation from other pursuits which must drain energies, vs knowing the books have to earn sufficient income and therefore a focus on quantity over quality? I feel like at one time she was in love with the world she had created and later on, perhaps only intermittently so; but I've no evidence whatsoever to support that suggestion.
I flip-flop back and forth on whether/in what way she wanted to 'be' Joey: I'm not convinced she necessarily wanted to be a wife and mother as Joey is - maybe, maybe not - as you say Emily she may have known very little of what that meant. I do think she wanted to have people react to her as they do to Joey - the way Joey is uppermost in people's minds even when she's not present, even when she's halfway around the world. The go-to example of wholesaleness, the definitive Naughty Middle, the definitive Best Head Girl. I adore the books and am super-grateful for them, but I suspect I would have found EBD a very trying acquaintance irl!