6 months

6months is the maximum recommended in order not to be under scrutinised or make them think you abandoned your LPR. do not stay outside the United States for 1 year or more especially if you eventually want to be naturalised

6 ms max.

at most is 6months ,if u are planning to stay for over a yr or two yrs outside the United States you must apply for reentry permit prior to your departure and ensure it’s approved with that you can stay 2yrs without abandoning your LPR or be seen as discontinued PR when you apply for citizenship.

is it 6months at a stretch or 6 months cumulatively while being LPR?

6 months at a stretch