You can pretty much count on your Angular project will fall apart after about two years if it has just modest complexity, and you are not maintaining carefully

You can pretty much count on your Angular project will fall apart after about two years if it has just modest complexity, and you are not maintaining carefully it. If you do not upgrade, likely one of the huge number of sub-dependencies of your project will stop being supported. Where stop being supported means it will have a severe flaw that will be start generating warnings, break the build, or it will simply be removed from the public npm-repositories. Technically you can protect yourself from this by having your own npm-repositories (ie. Artifactory), locking down npm, node, angular-cli versions and using a package-lock file.