Do you have all your assets in a single .blend file for your game? Or do you have multiple .blend files, one per asset?
If you store all/most assets in a single .blend file, what blender features do you use to make sure you don’t accidentally alter an unrelated asset while making changes to one asset?
A single blend per game? Good lord, no! That would be enormous! One per asset.
Level designers will stretch the definition of “asset” and put the scene model parts together, but I think that’s okay. It’s annoying when I’m in the engine editor and all the pieces have their origin at (0,0,0) regardless of where they actually are, but it doesn’t actually hurt anything.
@Sibbo from what I can tell from observing the artists I work with it’s mostly a mixture of both, assets that somehow belong together tend to be in a .blend file together, separated by scene collections.