I've had a green card for two years. My parents are in need of help abroad - father 94 and mother 89. I'm currently abroad (2 months) and would like to know what is the longest I can stay outside u.s. without having problems to get back to u.s.

If I am not mistaken, the rules have been amended to allow no more than 30 callender days outside of the USA per year. It used to be far more generous and was being abused by far too many people. But if that is incorrect someone will correct me. I got this information from someone that has a green card.

Get re-entry permit (I-131). Make sure you get approval before you go, then you can stay overseas for up to a year.

If you have 2-yrs green card (married a USC), I would recommend hiring someone to take care of your parents, or you will have big problem when file I-751 to remove condition.