QUOTE(raymaga @ Mar 13 2007, 01:20 PM)

The thing you have to remember is that once your GC expires, you cannot leave the US and re-enter, unless you have the NOA from the I-751 application, which extends your GC for one year, and includes employment and travel authorization.
So, you don't need to apply exactly 90 days before your GC expires, but if you plan to leave the US, keep in mind that the NOA can take up to a month to be received.
I hope this is true - we're going to be a full 6 months behind filing, and although my wife does not need to travel, we know that the status is automatically terminated as we didn't file I-751 on time.