How to automate reliable builds when Maven dependencies are only available for a limited time?

I have a Maven project which has several dependencies that:

1. Are hosted on a third-party artifact repository, which only holds the x most recent artifacts.
2. Are snapshot versions. (There are no releases available.)

Once I build my project, I need other members of my team to still build that same version of the project several years from now. However:

1. The dependency snapshot version I used may no longer be available on the third-party repository.
2. Even if it's available, the dependency may have been updated without changing the snapshot version number.

Is there a way to automatically create a shared repository of the dependency artifacts Maven retrieved when building the project for the first time? This would cause each dependency artifact to only be retrieved once from the third-party repository.

Set up a Nexus or Artifactory server in your company.

Add all the external repositories as remote repositories to that Nexus/Artifactory and run all builds through Nexus/Artifactory.

The Nexus/Artifactory will cache all the artifacts you have used, so no risk that some artifact is not available in the future.

For Snapshot version: If you really need to use Snapshot versions, use versions:lock-snapshots (https://www.mojohaus.org/versions-maven-plugin/lock-snapshots-mojo.html) before, so that you have reproducible version numbers.