Once the conditional permanent residency is maintained the investor and family members have to spend the majority of time in the U.S. The intent is for the U.S. to be their permanent home and their binding ties are in the U.S. For instance, bank accounts, tax returns are filed in the U.S. as residents, title to real estate. The investors and family members should not spend more than 6 months out of the U.S. otherwise upon their return to the U.S. the USCBP ( inspectors at the airport ) may make a presumption that the conditional permanent residents have abandoned their residency. In this case they will have to show their binding ties to the U.S. and this can be burdensome.
The Investor has to comply with various ways to show he or she is a permanent resident, like filing US Tax returns. While no set number of days is required, not actually residing in the US may cause issues in the future.