Q. Dear CMOS, Would you say “in the artist’s more than fifty-year career” or “in the artist’s more-than-fifty-year career”?
A. Though it’s rarely wrong to hyphenate a compound modifier before the noun it modifies (see CMOS 7.85), we like your first version best. According to the hyphenation table at CMOS 7.89, section 2, under “adverb not ending in ly + participle or adjective,” such compounds are usually hyphenated (e.g., “a much-needed addition”), but there are exceptions.
Specifically, a compound modifier with more, most, less, least, or very (among a few other adverbs) can usually be left open (e.g., “a more thorough exam”). Accordingly, if you treat the idiomatic phrase more than as a variation of the adverb more and fifty-year as a compound adjective (see “number + noun” in section 1 of the table), you’d write “more than fifty-year career.”