Use of possessive in "seven years' experience"

Question

I am attempting to write a personal statement at the beginning of a resume and am having a quandry as to how to write the following:

I am a super hero with seven years' experience in blowing out fires with my exhalation...

I assume that since the experience doesn't belong to the seven instances of years, this is incorrect use of the plural possessive.

How can I write this statement properly?

Answer 1

Common usage would be years' when talking about more than one year in a possessive sense. Seven years' means it belongs to a group of more than one year.

I am a super hero with seven years' experience in blowing out fires with my exhalation.

Compare with:

It had been years since I last blew out fires with my exhalation.

For reference: Purdue OWL- Plural Possessive center

Answer 2

To avoid using the apostrophe, you can write

I am a super hero with seven years of experience in blowing out fires with my exhalation.

However using the apostrophe and writing

I am a super hero with seven years' experience in blowing out fires with my exhalation

is fine, because it need not mean literal possession. Here the apostrophe simply means that the experience is related to the seven years in some way, much like in men's shoes or doctor's appointment.