Hello
I think there isn't rules how often you need to contact your CSA's!
It's enough to be a good sponsor, let your CSA's know what they need to do if you see that you can help them! If they working,and don't have any problems, that means you are a good sponzor! 2~3 Times in a week it's ok, asking how goes, any problem or maybe just to say hello so they will know that you are there!