Just citing Brandon because he mentions it all the time, and generally he's correct. I think RJ used narrative contractions slightly more often in the early books, but even then, not very often. My best guess is that he did it instinctively, and realized somewhere down the road that it was an aspect of his style, at which point it became essentially a rule. As for whether it's 'all right' to use any particular narrative style in general, there are a lot of differing perspectives in that regard, but RJ's narrative style is part of the feel of WoT. Brandon doesn't feel comfortable trying to imitate it, and I get that, but it does make a difference to some of us, and sometimes it seems to us that the differences are simple and not too difficult to address.