QUOTE(russian_armenian @ May 5 2008, 09:43 PM)

When we submitted (nov 2007), my lawer told his paralegal to make sure the package does not go 1 day earlier. But I have read some recomendations on other sites-and the lawers are talking about 6 months window. First, I thought it was a typo because all other info lawer said made sense. But now-maybe there is been some update into law. You are not loosing much by sending earlier-only shipping cost

There has NOT been an update to the law. An update to the law would require an Act of Congress, literally. Both houses of Congress would have to agree to the update, and then the President would have to sign it into law (or veto it and have his veto overridden). It takes many months for a bill to go through committee, be debated, be agreed to by both houses, etc. During the many months, all the news sources that cover anything related to immigration will discuss the debate.
In other words, the Immigration and Nationality Act doesn't change before we know about it.
You MIGHT lose much more than a bit of postage by sending it earlier. If you read the case law (some decisions are available
here from the USCIS), you'll occasionally find cases where a person's status is questioned after the fact. Sometimes, if the immigrant made a procedural mistake and the USCIS didn't catch it when it happened, the law can be enforced against the immigrant at a much later date, sometimes when it's too late to correct the error.
The nightmare scenario is that they accept your I-751 when you file it, and it waits for 9 months to be adjudicated, and then the adjudicator says "hey, this is not approvable because it was never filed within the correct window -- I'm going to deny it". You as an immigrant might be able to appeal to someone's sense of justice, but as far as I can tell, I don't believe the law will be on your side.
I don't know what the likelyhood of later problems is. For all I know, there might even be a provision hidden somewhere in the law that absolves the immigrant of any responsibility if the USCIS makes this particular error. That would certainly seem reasonable and just, but I know there's no such law generally -- immigrants are often penalized severely and unfairly for USCIS errors.
And in the scenario we're talking about, it's the immigrant's error that starts the cascade of problems -- the law clearly does require the immigrant to file within the correct timeframe.
If you think I'm overreacting and being overly conservative, feel free to ignore this whole post. I'm not a lawyer, and I could very well be completely wrong here.
But I still think the safest thing to do is to file during the window when the law says you're supposed to file.