When I was working, I had several databases. Some reusable functions/procedures etc started to appear in every database. That's when I learned of Library databases. I saved these as .mda and placed them in system32 and they were always available.
Now I have only 1 or 2 databases, just to do a few things in response to posts/posters. So I could easily put everything in the one/two databases, but thought I'd keep some routines separate.