It is now 90 days. There's a great "how to" page that is stuck toward the top of the Restaurant board. They have some good tips on CRT that should also help for PSB.
Another option is Cinderella's Gala Feast. While she is the only princess, this is a dinner and doesn't seem to be as in demand as others. DD and I did this one as well as PSB and, other than not seeing as many princesses, I preferred the dinner. It felt more relaxed yet elegant - if that makes any sense. Also, the food was so much better and we didn't feel jammed into a corner as we were for PSB.
Slightly OT - I have to say I was a bit irritated by the less than ideal locations of the tables for 2 in many of the restaurants. We seemed to either be in a corner (Chef Mickey's and PSB) or right next to the door leading to the kitchen (O'Hana and 1900 Park Fare). For all of these we had PSs so it's not like we were walk ups and were just happy to get a table.