It has long been established that doing FP ....
early helps. Especially with processing window shrinking to 6 months or less, waiting till scheduled date may just be a waste of time. INS does not care when you do your FP. FP is a milestone that has to happen before your case becomes adjudication-ready. Hence, sooner you do your FP, earlier your case becomes adjudication-ready. In months gone by, cases took so long that doing FP a month early really did not matter. Your case would sit on the shelf waiting for assignment. Classic case of hurry up and wait. But, with much faster processing now, that is no longer the case. Just do it early.
Oakland has been known to not be early-FP-friendly unless things have changed in the last month or 2. San Jose on tha other hand has been know to be early-FP-heaven. Again, unless things have changed in the last month or 2.