You cannot simply drop this in a mailbox. You must hand it to a retail associate at the post office. If you try to mail it, they will likely reject it. This requirement isn't always clear on the form itself, leading to wasted trips.
The printable USPS Change of Address form is a functional tool that saves you a dollar, but it costs you time. printable usps change of address form
After 12 months, USPS stops forwarding. You must notify all senders directly of your new address. You cannot simply drop this in a mailbox