GREEN CARD HOLDERS: I am not a visitor, but a resident of wherever I am.

I have a green card and plan to travel for 1-2 years. Can I travel for 6 months, then come back, then travel again and come back after 6 months or will it be an issue?

Yes, you can travel in six-month tranches if you want to, and if, every time you return to the US, you can convince the CBP officer who welcomes you that you are in fact still a US permanent resident. To do that, you have to show that you still are rooted in the US through things like a permanent mailing address, bank accounts, valid state driver’s license, etc, etc.

The alternative, as others have mentioned, is to request a re-entry permit from USCIS before you leave. That will let you stay out for up to two years and then return.

Another alternative is to apply for an SB-1 returning resident visa when you are finally ready to return home. But it will be up to the consular officer to decide if you had to stay away so long, and for some convincing reason could not return sooner.