For me the best way to stay in contact with my PSAs and CSAs is by sending them mails through our PSA/CSA mailers once a week, that is the reason why we are awarded 30 versapoints weekly by doing it.
You can also send your mail to their personal e-mails if you wish to stay in contact with them, also by sending team mails through your stream portion.
Too much contact with them is not good too. Some joins for No reason at all, they just happen to sign in. Good luck.