Open window to file petition-what is it?

Hello to everyone
I am reading this forum for a long time. I noticed that in some posts inspite of retrogression some people are talking about an open window when you can file a petition for a green card. Others get mad and say that you have to wait in line.
My question is - what is this open window that magically appears approximately in July and some nurses are in a hurry to file and some unfortunately miss it and still have to wait like others. Somebody knows?

Here is one of some examples that I was reading:
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Originally Posted by anfe

Suzanne

I graduated from a US [COLOR=green! important][COLOR=green! important]nursing [COLOR=green! important]school[/color][/color][/color] in May. Wrote and passed the NCLEX in July 2008. I did not apply during the window in July. So again, does it even make sense to appy for the I-140 now and wait in line? For those of us just getting ready to start the paperwork, with over 300, 000 plus applicants jamming the system ahead of us, what should I do now?
I am on OPT till Jun 2008. I am not from a high applicant country.

Does it makes sense paying for an attorney to start green application that is likely not going to go nowhere for ???? # of years? or should I just start the process, at the least?

tks

I think that you mean that you just passed the NCLEX exam this past July, 2007. Which country are you actually from? You can send it to me in a pm if you do not wish to post it here.

Not sure what is going to happen with the visas by the time that you need things to be available. If fo some reason, there are none, you will need to continue with your [COLOR=green! important][COLOR=green! important]studies[/color][/color] to maintain the F-1 so that you can remain in the US. Your visa will expire 60 days after you complete your OPT, you maintain the F-1 while under the OPT.

If you definitely wish to work at that facility, I would go ahead with the I-140, as that has specific time requirements with it that need to be completed before the I-485 could ever be submitted, especially if they only open with a short window of time again.