Hi @nssouzapeters, thanks for being a loyal Trend Micro product customer!
To answer your question, since Internet Security and Maximum Security are two different product editions, their license period cannot be combined. If you renew your Internet Security before your expiry date, your subscription will be automatically extended to the number of years purchased but it will not change product edition.
If you will like to protect your more devices with Trend Micro Security, here is our recommendation:
Purchasing a new license for your other devices.
Upgrading your subscription to Maximum Security when the current license expired.
If you want to upgrade your subscription to Maximum Security when the current license expired, we suggest disabling Auto-Renewal by the following step first. Frequently asked questions (FAQs) about Auto-Renew - refer to "Disabling or Canceling Auto Renewal"