I have a few registered trademarks that I put into place almost 10 years ago. Once you trademark something, you have to pay a renewal fee, and prove that you have used it, after 5 years and again between the 9th and 10th year.
A few months ago, I started getting notices about an upcoming renewal. I had assumed that the notices were bills from the Trademark office because they looked very official and had all my information on them.