Hi @Julian Steven Molina Campos ,
as far as I know there is no time limit on Microsoft Entra ID Free edition.
Source: Microsoft Entra service limits and restrictions
The security defaults for MFA don't need a license in a Microsoft Entra ID Free edition:
All tenants are entitled to basic multifactor authentication features via Security Defaults.
Source: Available versions of Microsoft Entra multifactor authentication
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten