I've worked in AFG since 2003.
You need to meet the physical presence test to qualify for tax free income. That means you have to be overseas 330 out of 365 days. Nine months isn't going to make the cut. Once you get past the physical presence requirement, which can go across 2 years, your tax free income will be pro-rated based on the number of months (days) you are out of country.
For example...you start working 1 JUL 2013 for a full year until 30 JUN 2014 and you come back to the states. You meet the physical presence test for tax free income up to 90K plus (whatever it is this year), but your tax free income, not eligibility, is based on a the fiscal year of 1 JAN - 31 DEC. Since you worked 6 months in 2013 and 6 months in 2014, only 50% of your income is eligible for the tax free benefit. Let's just say you made 80K for those 6 months in 2012...only 40K would be tax free. Same for 2014. Now if you did multiple years into 2015 or beyond, you would get the 100% tax free (up to 90+K) for all full fiscal years.
You can also claim residency for the country you work in and that trumps the physical presence test, but different countries have different residency requirements.
I recommend just having full taxes taken out so if for some reason you don't meet the physical presence test, you won't owe Uncle Sugar an ass load of money.