I got my GC throught marrige to the American citizenship. Right after I got stamp on my PP I applied RP next day and left the country next day ( in 2006 they didn't require FP) and returned the US after 23 months 2 weeks. At that time I came back with my wife and my kid who was born abroad and also get Amercian citizenship at the US consulate. I got no trouble at all, the officer just asked how long I'd been out the country and then let me in with no futher question. After this trip, I was living in the US for 6 months and then left again and came back after 6 months , this time I came back just by myself without my wife (she got pregnant, again we plan to give birth the second kid in my country) and you know what? It took me about 30 min at the port to explain the reason I lived abroad that long, while I was answering the question, the officer keep typing on the computer likely he's searching something on that and then he wrote down on the custom paper 3 letters "BGC" ( back ground check I guess). Not yet, after getting luggage and getting out at custom point, the custom officer (or INS officer I dont know, they all wear the same uniform) take a look at the paper with "BGC" on that and took me to the custom check point to open all my luggage, my wallet and everthing in my pocket also was taken out and search carefully such as Im a most wanted on the world. While she checked my luggage she kept asking me alot of questions just like the questions the officer at the entry point asked. Finally, she told me that : do you know if you go in and out like this, the officer will take your green card. Of course I could get in the US at that time but I was really nervous about all this stuff. Again, I was living for a few weeks and left the country , this time came back after 4 months with my wife and kids (second kid was just 2.5 months old at that time and also got the US passport at the US consulate), I was so nervous at the port, showing my passport and GC following all the US passports of my family and suprisingly just 1 question asked regarding to the lenght of traveling abroad and that's it.
SO, to make life easier, bring your family with you