Phrasal adjective hyphenation
The same phrases are unhyphenated when they come after what they modify—for example:
His wit was razor sharp.
The characters were over the top.
His personality was larger than life.
We make exceptions for phrasal adjectives beginning with -ly adverbs. These are conventionally unhyphenated—for example:
poorly run bank
closely held positions
When two closely related phrasal adjectives have similar ending elements, remove the ending element from the first phrase and leave the hyphen, like so:
the four- or five-year-old girl
Phrasal adjectives and units
When a phrasal adjective denotes an amount, a number, or a duration, the unit is singular—for example:
the four-story, 50-unit complex