Monolithic Reference Collection, vs Per Paper Reference Collection, or Both? When managing References,
seem to me to be two-ish, options:

Either for each Project, I maintain a database of the relevant resources (In say a bibtex file),
and for each new piece of work I start a new one.

Or I maintain a single "Monolithic" collection of resources (still in a bibtex file),  for everything I do, and I carry that around with me for years.

There are some in-betweens, such as having a Monolithic Collection, which I copy references from at the start of a project into a Project Collection, which I then use (and update) during the project, then copy either all or some of it back into the main collection.

What are the Pros and Cons of each approach?
Am I thinking about this in the wrong way?
I usually go with a single database, arranged in folders and/or tags. So the references are present one time, and then I just move them around according to what I need to do.

If you have separate databases, you risk to duplicate records, and save the same reference many times.

This also depends on the type of system you use: Zotero and Mendeley (the tools I mostly use) go with the single-db solution arranged in folders and tags, whereas EndNote allows to create separate libraries.