>> Another, arguably better, approach is to automate the processes involved and allow self-service provisioning.
Personally I really, really, really do not think that is in any way an answer to the problem of end of life management for virtual servers. I'd argue exactly the opposite - it means business users can provision themselves a server on a whim, not tell anyone, and then just forget about it when they change their mind.
It's bad enough if servers are centrally and you can record their creation, but when the techies find themselves with no free resources and a gazillion unknown servers, then it's going to be even harder.
Unless part of that automation system requires the 'owner' to log in and refresh their server from time to time - without which it will just get turned off automatically. That is often the *only* way to deal with some of these servers (whether real or virtual) - turn them off and see who (if anyone) complains.