Really it doesnt matter. Its just a question of how you prefer to work. Or what the end product is.
For example if you are exporting the character to a game engine and need things lite, then fewer shaders can be better.
However, if you are rendering in Maya, then do what works best for you.
Typically for me, I'll group objects with similar shader properties together, then split them up further by interchangeable parts.
So let's say, body, Eyes, clothes are three different materials, each with its own udim sets. But I'll go further and split up the shirt and pants into two different materials, that way when I wanna shake things up I don't have to mess with both material sets.
Again, whatever you want. Hope this helps.
