We have applied for green cards for our parents - we are citizens.
Our parents are visiting us in the US. Their I-94's are about to
expire. Is there anything to be done? Everything I've read states
that they have to stay in the US until their I485 is processed and
should get advance parole to leave. But I have not seen any details
regarding what (if anything) needs to be done to make the stay
legitimate. I.e., is the fact that we have applied for a green
card sufficient, or do we have to keep renewing the I-94's until
their applications are processed?

Thanks,

Sriram.

I'm not an expert, But as far as I know ,they only give up their I-94 if they leave the country, they don't have to keep renewing it. Since you have filed their I-485 I suggest they stay where they are in the USA and wait to be processed, they don't have to do anything more. They are stuck in limbo like a lot of us waiting for be approved. If you have received any receipts, proof that received your payment for fees from BCIS that is proof that they have a case pending. Are they planning to leave the USA on advance parole? then that's another story.