Heck - let me repeat once again. You can make any shot as big as you want. One of the most negatively influential images in history was the partial frame of a rather poor 35mm exposure routinely enlarged as much as forty FEET across - the Marlboro Man billboards. That size enlargement was perfectly appropriate for a "normal viewing distance" of a hundred yards away by a vehicle speeding 70 mph down the freeway in the haze of their own cigarette smoke.
But if you want a reasonably crisp enlargement at say, book reading distance, 8X is about the limit, and quite a bit less for my own nose-up with reading glasses expectations. For example, I never print a 6x7 cm image beyond 20X24 inch print size, even under the best of circumstances; rarely more than 16X20 when black and white rather than color film is involved. And I have exceptionally precise printing equipment capable of higher detail resolution than anything inkjet.
Yet that doesn't make me discount what others are doing with a different kind of visual strategy in mind, or for quite different display purposes. What works, works. But I don't think any mere generic answer is worthwhile in this respect; no one shoe size fits every person either.
But the standards of "Curators"nowadays?? (barff - big for big's sake is all they seem to think about - megabarf).