I've always assumed that models should be comprised of a single mesh. Is this true? Or can I conceivably create a model with multiple meshes, some lumped together?

Examples: Character mesh with separate eyeball meshes in the sockets, and possibly some separate meshes for "accessories" or "protrusions" or whatever? Building details.

thanks

Depends on the use.

There's nothing wrong with using multiple meshes. However, you may encounter lighting issues...

Does anyone here have any sort of guidelines or wisdom on when this might be desirable and undesirable.

I've seen it done for clusters of rocks, for instance. And in some of the tutorials I've seen for Blender and Gmax (years ago), I noticed that they'll basically cluster a bunch of meshes together to form a character.

Other than possible lighting issues, does it cause problems with animating or anything?