How long does one have to serve on the Grand jury in Suffolk County, NY?

I received a summons for the GRAND jury in Suffolk County, NY. I have read conflicting reports as to how long a grand juror typically has to serve. I've heard everything from 9-5 five days a week for a month, to once a week for a year or more, or 4-5 times total in a 3-4 month period.