Why do you need to communicate with them? When the need rise up? Primarily because you want anwers, help and guide. New affiliates will have questions in their mind about SFI, help to get started, and guide, even months after you joined. And ofcourse you may ask how they are, share useful information and ideas.
So, how often? No, it should be : When?
When you need it, when you want it, don't hesitate to contact them.