Case

My conlang used to have a really really elaborate case system, with
probably about twenty five different cases.  Recently I decided to
change this to just a few:
nominative
accusative
dative
genitive
prepositional(?)-does anyone have a better name for that-its for use
after prepositions, obviously

I'm just curious, but those of you who do use case in your language, how
many do you have?  Where does it go from being "cool" to just plain
unworkable?

Nicole
--
"What's it going to be then, eh?"