回复：回复：Losing job. Urgent question about 485. xiaobaitu and

H-1B'S are initially issued for three years and can be extended for another three years, for a maximum of 6 years. The clock starts ticking from the date of arrival and not from the date of visa issuance. Moreover, it is based on time actually spent in the U.S. on H-1B status; it is not based on the validity of the visa.
Therefore, if you spent significant amounts of time outside the U.S. during your six year stay, it is possible to "recapture" some of that time by extending the six year maximum. Please be prepared to provide evidence of significant periods (i.e., more than one month) of time spent outside the U.S. in H-1B status if you want to apply for an extension to get the benefit of time spent outside the U.S.
After the 6-year limit on an H-1B visa is reached, an individual can leave the U.S. for one year and re-enter on an H-1B visa. The one year abroad does not have to be in your home country or country of last residence.