is there stay time restriction for multiple entries? fastEatSlow2006-11-03 01:53:51

Hi,

My parent-in-law got half-year visa with 1 year multiple entries on 2/27/2006. They came to US on March and back to China and came back again at Sep. 2006. They will back to China next Feb.

Can they entry again for another half year before 2/27/2007 ?
Or,
All the multiple entries must be within 1 year time frame ?

Thanks in advance for your answer.