Good question, what I do is look at my Genealogy report, you can keep up with where your affiliates are at and if they are above the green line.
You can also see if they have even Confirmed Registration, Completed Affiliate Profile and you can see if they have even Whitelisted mail. If they have not done these action then you should email them, send them a welcome card and explain how this works.
Talk to your Affiliates one by one and get them duplicating.