Yeah, actually, that is partially why I DON'T have edition fatigue; I use all of those books as sources of inspiration, & even seeing things recapitulated can help me grind down to what I like about it; how many monsters have you been like "oh, new art, now I totally get it!" 'cause it happens to me like, every new book. & then yeah, I keep 'em. Especially monster manuals, those are the most system neutral.