Filed as a resident since coming to USA
When I arrived in the USA in 1993, on an O-1 visa (dual intent), I started filing taxes as a resident because my understanding was that I was 'residing' here. O-1 visa have no theoretical time limit (they are not limited to, say 6 years, total) but you do have to get them extended every year after the first three. When we got our GCs, we continued to file the same 'resident' style 1040. So, in 13 years we have filed 12 tax returns as residents. I have not lived anywhere else during those 13 years, nor earned any income abroad.
This was all based on the assessment of my tax accountant starting back in 1993. Now, I am not sure whether we should have filed different tax returns for the years prior to obtaining our GCs. When we filed our 485s, we of course provided several years of tax returns, which were clearly 'resident' style 1040s. Our GCs were approved without RFEs or interviews.