As it happens I've recently upgraded a 2 year old project with both node and C#

It was open much the same in both. If you're happy using outdated and unsupported components with security issues AND you can get hold of the right version of the dev tools and plugins AND your hiding environment still supports the old platform, you can maintain the old version with minimal change. But should any professional developer do this?

It depends.

In domains where software is expected to run for years, if not decades, it's common to archive the entire toolset, along with libraries and SDK's in case you need to fix a bug/add a feature 10 years later. Obviously, in this case you can't have dependencies sitting somewhere on a server you don't control.

There are also situations where this is forced by regulation: you need to recreate build xxx.yyy.zzz 7 years after release because a customer reported a serious bug and it needs to be reported to the relevant regulatory agency and investigated.