I do think it might be a bit unrealistic at 6 weeks especially.
This is the bit that I still don't really get... as I said my MIL raised 5 children this way so they obviously didn't die (though I think they have attachment issues- but that may not be related to their night time feeds) but it seems so young to impose such a routine IMO. Hence why I wondered if it's possible to happen naturally for demand fed babies.