My managers are asking, before green-lighting a new project, how much people (resources) will it take after the project is done, to maintain it. Ie: fix bugs, deploy new features on demand, adapt to changing business processes, etc.?
What I am able to evaluate (based on history of other projects) is avg. number of bugs happening in production. But I don't see how I can evaluate processes changes, new management requests, new business opportunities.
What scrum metrics can I use to calculate this. Or is there any rule-of-thumbs I can rely on?