The obvious answer is "regularly". Which then poses the question of what regularly means.
Make communication to the point. Perhaps you are asking questions and that is good, but is it a question that has been answered elsewhere?
Do not bombard them with emails, but allow them to reply and answer your points. Treat it like a conversation.
Is your sponsor an A2A friend? Do you communicate outside SFI on something like Facebook, as many affiliates do?
If you have a good sponsor they will be sending out a Team mail and sending advice. If you are a good affiliate they will notice you and be keen to give you personal attention and help develop you.