I also use more than one vault:

• cooking recipes (read-only, used for reference, contains all recipes from Paprika, a recipe app)
• Microsoft Writing Style Guide (read-only, used for reference, synced from the official Microsoft GitHub repo)
• Tasks and everything synced from Readwise; I read and review books mainly for publishers so it's super handy to keep book notes and when to publish what in the same space
• dumps from projects with a lot of text that allows me to use the vault as a kind of database