Install NWDI as a separate instance - Need Advice

Hi All:

Myself setting up a 3 systems (Dev, Qlty & Prod) landscape in my current project.

Now I really want to understand and know the advantages and disadvantages of having NWDI as a separate instance rather than having it in Dev, Qlty (or Prod) Systems?

Why it is imp to have only in Dev system? Or how many DI instances do i need to have?

Thanks in advance,

MS