As noted, there have been several scenes you COULD mean, but there's at least one big one in KoD.

I can't say it's BETTER, but I concur with those who say re-reading the whole thing is probably unnecessary. If it were the last book there'd be a greater chance of some minor detail from TGH proving pivotal in the final volume, but as it is, save your re-read for the last book. I probably won't even do one, since I've read TGS twice in the last year, and going back beyond KoD is just too painful to consider. If you're going to do a full re-read, I suggest just skipping from ACoS directly to KoD (which kinda defeats the purpose of a re-read. ) Otherwise just re-read the last couple if you need a refresher.