When they "Opt out", we'll know they're not serious. Until then, we can't know for sure!
I have a PSA that had not logged in since 4 days after she joined several months ago. I sent her an email a few weeks ago letting her know she was the sponsor of a very active PSA
(BTL, to be exact!).
It took a little while, but now I see her smiling face on my Movers List every morning:)