The phrase "a six year duration" is correct and usable in written English.
It can be used when specifying the length of time something lasts or is expected to last.
Example: "The project is expected to have a six year duration, after which we will evaluate its success."
Alternatives: "a six-year period" or "a duration of six years".
The original erection of the Bay Lights, a roughly $10 million project that was supported by high profile (and high net worth) San Francisco techies including Marissa Mayer, Ron Conway, Matt Mullenweg, and others, has a two year duration that will make the lights go dark in March 2015.
In Texas, no matter how long a couple is married, the party receiving alimony is limited to a maximum order of $2,500 per month for a three year duration and only if the marriage was 10 years or longer.
This paper documents the successes and failures of recruiting over 2,000 women aged at least 70 years and at higher risk of falls or fractures onto a placebo-controlled trial of six years duration.
Compared to patients diagnosed with hypertension over the past five years, those with a five to ten year duration of diagnosis of hypertension had greater chance of reaching overall targeted BP (adjusted odd ratio [AOR] = 1.62; 95% confidence interval [CI] = 1.07-2.44).
When Heraclius "went out into the lands of the themes" in 622, thereby undertaking a struggle of seven years' duration against the Persians, he utilized the third of his sources of strength: religion.
Following the completion of their midwifery training, the CMWs were required to sign a service bond of three years' duration, whereby, they pledged an amount of approximately PKR 300000 for service in community and their diplomas were also held in escrow for the duration specified.
To achieve this ascent, the students have to undergo, first, a preparatory schooling of ten years duration in the 'liberal arts': arithmetic, geometry, astronomy and theoretical harmonics (518c 531c).
Of their 211 patients with prior peroneal nerve trauma and a fistula of over two years duration, only 28 (13.3%) had persistent physical signs of nerve trauma.
