Hyphens for compound range in "He will be at the job for one to two years"?

Came across something written like "He will be at the job for two to three years." A colleague suggested it should be "two-to-three years." I disagreed. I see the rationale for a compound here, but my reasoning went something like this: the elements of the range can stand independently (i.e., he could be at the job for two years or three years).

This stands in contrast with with something like an eight-to-five job, where an "eight job" wouldn’t make sense on its own, so hyphenation is called for to express a compound range; in other words, hyphenation is appropriate when the expression could only make sense as a distinct range. I’m having a bit of difficulty trying to articulate a rule about this, though, and my rationale seems a bit pedantic because I definitely see that the numbers are a range modifying "year."