I have been in the same boat as you when it comes to side projects, but I'm curious about your use of the metaphor of "sucking the marrow from the bones" because that metaphor is typically used to describe completion to an extreme. For example, if "eating an animal" was your metaphor for working on a side project, I think that a more apt extension to that metaphor would be "leaving meat on the bone" rather than "sucking the marrow from the bones". However your metaphor refers to the marrow as "learning-marrow" which confuses the larger metaphor that is "eating an animal".

Have I completely misunderstood the extended metaphor you were trying to use?