Number of Classes in a Namespace - Code Smell?

Question

I have a C# library that's used by several executables. There's only a couple namespaces in the library, and I just noticed that one of the namespaces has quite a few classes in it. I've always avoided having too many classes in a single namespace because of categorization, and because subconsciously, I think it looks "prettier" to have a deeper hierarchy of namespaces.

My question is: does anyone else consider it a "code smell" when a namespace has many classes - even if the classes relate to each other? Would you put in a lot of effort to find nuances in the classes that allows for subcategorization?