[cris-ward]

From someone who briefly used 'bower', which was JS dependency management using git, relying on git is a lot worse.

Github repos can vanish, NPM will only let repos be deleted if they have no direct dependencies also on NPM. So you have some guarantees your dependencies wont vanish.

[saturn_vk]

If the repo was used at least once, it will be cached by the default proxy. At that point, deleting it will have no effect on builds