If you originally purchased a Malwarebytes Anti-Malware license before March 24, 2014, you have a lifetime license (often, but not always, downloaded as “Malwarebytes Anti-Malware Pro”) that does not require renewal or any additional payment. There were a limited number of additional lifetime licenses available after that date through promotional offers.
If you are receiving renewal notifications, it is because you purchased renewable licenses in addition to your lifetime licenses. These renewal notifications apply only to your renewable licenses.
You can use the My Account portal to review information about your license(s), including whether the license is a lifetime license or a subscription license.
See How do I set up my Malwarebytes account? if you have not already set up your Malwarebytes account.