Continuous integration (CI) is a software engineering practice that promotes frequent code integration into a shared repository, improving the productivity within development teams as well as the quality of the software being developed. While CI adoption has gained traction, studies have examined its effective implementation and associated challenges. The idea that multiple contextual factors influence the adoption of CI prompts an exploration of suitable descriptive metrics for describing the CI practices employed. This paper aims to explore the metrics that best depict the level of maturity of a project, addressing the question: "What metrics can be used to describe the maturity level of a project?". With a lack of a comprehensive maturity framework, we leverage GitHub's API in an attempt to analyze various metrics to be used to create a framework for filtering projects. Our findings indicate that project maturity cannot be captured by a single metric, but rather a combination of metrics reflecting different aspects throughout the project's lifecycle. Activity levels, including commits and pull requests, popularity indicators like stargazers, forks, and contributors, as well as repository size and age, emerge as primary indicators of maturity. By combining these metrics, a unified framework for categorizing mature projects can be established and further developed.