One of the issues that sometimes crops up when talking to customers about Installation Manager is some confusion around the different versions, and whether there is a need to maintain the older versions of Installation Manager in their environments. I've seen customers tie themselves in knots trying to match versions of Installation Manager to versions of the various products they need to maintain.
The thing that simplifies all of this is that we try VERY hard to keep Installation Manager backwards compatible. This means that (to date), the latest version of Installation Manager can install any product or version of a product that is Installation Manager based, no matter what version of Installation Manager the product originally shipped with. The best practice from an IBM perspective is to update Installation Manager regularly, and use that updated Installation Manager to maintain and install the products in your environment.
While I can't promise that this behavior will stay the same in the future, it is our intention to keep Installation Manager backwards compatible to simplify your deployment experience.