You don't have to do anything if the info they send you on a card is correct. (Basically if nothing has changed since you bought it, do nothing.)
no, you dont do nothing. you have to sign it and mail it back to them.
The triennial card is a probe to see if the address is correct. If it gets returned then will begin a process that could lead to cancellation of the registration, which is a new deal thanks to the Department of Homeland SNAFU.
Being that I moved - and I SWEAR I updated my address but I must have missed the registration - I got the dire warning cards (forwarded to me by the USPS AND the FAA based on the USPS address correction (Doh!)
I replied with certified, return receipt.
I talked to the aircraft rep at Oshkosh to verify the plane was still good. At that point they didn't have the new address, whcih I has sent just before leaving, but I wasn't far down the cancel trail. She said if the registration is canceled, it's a very, very, very tough process to get it straightened out.
Oh. And the aircraft registration branch doesn't have an online change of address like the airman branch does, sorta like how you can request your airman records be kept private but not aircraft records.
You are allowed to put the registration at an address other than your home (although now (smelling DHS again) you also have to provide your physical address, which I hope is kept private.
BTW, when you check N numbers you can see those with "Triennial card returned as undeliverable," which are ones that are gonna be available soon. I gotta guess a lot of cool numbers are held by people and aircraft long dead.