It may be better to think of the time in the US requirement the other way: the longer you spend outside of the US, and especially if it’s in one large chunk of time, you risk having the green card revoked for abandonment. In addition, when you are ready to apply for citizenship, your time spent in the US versus outside of the US is considered again.
The U.S. permanent residency requirements apply to the investor whether in the U.S. in conditional permanent residency status or unconditional permanent residency status. To maintain permanent residency in the U.S. it has to be the investors intent to reside and live in the United States for the majority of time as well as to have proof that they are residing in the United States. For example, proof of filing tax returns as a U.S. resident, U.S. Bank account statements, drivers license and title to real estate my show the intent of the investor to reside in the United States permanently. It is always better not to be away from the United States for more than 6 months otherwise upon return to the U.S., at the port of entry, U.S. immigration inspectors may make a presumption that because the investor has been away from the U.S. more than six months the investor has really abandoned residency in the United States. Therefore, if the Inspector's ask questions to the investor about their intent to be permanent in the United States the investor may show proof of residency with documents that we have referred to above to show that the investors have maintained their U.S. Residency.