Hi @acspencer2011, welcome to Trend Micro Community!
First of all, Registration requires a valid product serial number and a valid email address for renewal and other legal notices. Once you activate your subscription, no matter you use on 1 device or 2 devices, the expiry date is always the same unless you renew your subscription.
Also, If you only want a basic package (protection for to 2 PCs...etc), the following product might meet your expectation. After your license expired, you can purchase a new license instead of renewing.