I know what you mean, Q. I act like I'm preparing for move too. Although I don't have the forms ready now, because in case they change them I don't want to risk to make a mistake by sending the old ones instead, which might make things complicated more than necessary for me
But hey, that's just me. I have a travel organizer and keep the documents and other stuff from my last US visit in it. Like Enterprise car rental card, SSN card , international driver's license, passport obviously. Even a US SIM card I ordered from eBay for a dollar or so and never used it yet, haha. Funny maybe, but I like to take a glance on the organizer from time to time and think I'm preparing.
Talking about preparation - in case anyone needs a US PO Box for the actual green card, I did a quick research and found that USPS fees for a PO BOX in New York starts at around $20/three months. That's just USPS and I didn't look for other services as I would probably use their service. I cannot post links yet, but you can copy and paste poboxes.usps.com to your web browser and check the rates for the area of your choice.