In terms of an actual number, there's no such limit. What matters is the following:

• Does each additional mass serve a purpose

• Do the masses wrap around the underlying structure (including previous masses) - specifically in terms of how their initial silhouette has been drawn.

As far as the otter demo goes, it was done quite a while before I really started pushing the additional masses more and more, so it shows less use of it overall. These days I push the concept of simple sausage chains as a base structure/armature, and then achieving all the complexity and bulk we're looking for using additional masses.

You can see just how many I employ when breaking down this informal puma demo to get a better sense of what I mean by that. Again, pay careful attention to how each individual mass wraps around the underlying structure, curving its silhouette to really cling to the forms it's attaching to.