PSMail payment allows you to renew account for multiple years, i.e., allowing you to renew your account for more than one year at a time. Please visit https://mail.psmail.net/newaccount/multiyear.php
When you are prompted enter your primary PSMail email address (do not use your alias). You will see renewal years option which you can use to change the number of years to larger than one. A nominal discount will also be applied during checkout for your multiyear renewal.