Sure! I keep separate vaults for a couple of reasons:
First, I need to keep my work and personal data separate.
I work in software development, so I manage projects that have information private to my employer that I don’t want on my personal computer. Likewise, I have personal notes that I don’t want on my work computer. So I keep a work vault on my work computer, and a personal vault synced to my home computer, phone, etc.
I also keep a third vault, called “Reference” that contain technical notes that are useful both at work and at home, but don’t contain any info private to either. I keep a copy of that vault on both my home and work machines via Obsidian Sync (my employer permits this).
An advantage of this approach is that I can use separate accent colors for each vault, so I always visually “feel” where I am and am less likely to accidently put the wrong info in the wrong vault.
Second, I like to reduce distraction by keeping focused vaults.
Outside of work, I like to develop stories and tabletop role-playing games, and I have to maintain a lot of notes in order to keep all the people, places, and plots straight. I keep a separate vault for each game, so that when I’m thinking creatively about one world I’m not distracted or confused by notes about a different world. I’m pretty distractable, so this is very valuable for me.
Keeping separate vaults is especially helpful when different characters or places happen to have the same name; there’s no chance of overlap. It also allows me to keep separate schemas for each vault; in one world I might need to track, say, languages carefully; in others I might not care about that at all, but need a very detailed timeline across different ages.
There is a cost to all these separate vaults, of course; if I have references or tables or languages that are common to more than one story, I have to keep those in my personal vault or else keep multiple copies. But this doesn’t happen too often, and the value of focusing my attention and separating concerns far outweighs the cost of occasionally managing multiple resources.
Well, that’s probably enough rambling for now. Hope this helps. 