Again, it's not good or bad to do anything if it's needed. But you probably don't need very many static variables, in general (I've never had the need for more than 2 or 3). Static methods only take up the memory for the compiled instructions of course, just like any other code.
I don't remember offhand how the garbage collector treats static variables - I would imagine it treats them like any other chunk of memory.
-Nerseus