This is all I can tell you since it will be our first time in May staying concierge.
I have PS's for Cindy's on 5/2 at 8:30am(which I realize I'm lucky to have) I got these the oldfashioned way, speed dial! But I really wanted them for 5/1, I've asked concierge to try and get me a PS for then. This was their gracious reply; For the request to book a priority seating at Cinderella's Royal breakfast and Chef Mickey's we have placed your request on the concierge waiting list. We will continue to check availability daily for booking.
So I think that is great! Like I said before, I already am lucky to have what I have so I guess I'm not really in the place to be disappointed if it doesn't come through for the 1st.
I know I've read on these boards how people have had concierge get them PS's for Cindy's last minute, but I really think it's more luck of the draw than anything.