We have done BB twice - most recently last week. You can call 60 days in advance for PS, but it is not mandatory to call that early. When we went two years ago I called 5 weeks in advance.
It was recommended to me to get a PS at 11:30 right when they open, which minimizes waiting. Remember that PS does not guarantee immediate seating, it just gets you seated a bit faster.
We had 5 in our party last week, and wanted water side seating (highly recommended - you can see the POTC boats from there). For parties of more than four there is limited waterside seating (two tables I believe) and although I requested that it did not guarantee I would get it.
We showed up at 11AM but they did not start check-in until 11:15. At 11:15 I checked in and reminded them of my waterside request. I saw the CM write down "11:16" by our name, so they were tracking who made requests and when.
We were seated at about 11:35 and got a waterside table.