Normally you would contact them whenever you cant find an answer or explanation on things regarding SFI.
Also some sponsors do have rewards/incentives for their affiliates, you may want to contact them if you feel that you are qualified for those incentives but haven't received it yet.
And of course, you can contact them whenever you feel like it, just make sure it is related to SFI - specially when you are using TEAM Mailer. Spamming isn't allowed, and really is, unpleasant.
