It depends on if you're having a wishes wedding or escape wedding. For a wishes you can book it 16 months..if your reception is anywhere else other than a convention center. If that's the case than you can do a tentative hold at 16 months and sign the contract at 12 months. And I believe if it's escape you can tentatively hold at 12 months but you have to wait til 8 months out to sign the contract. HTH
Just so you know SBP can not be contracted til 8 months out. The rain/backup site is a convention room so it can't be held for wedding til 8 months out. You can hold it at 12 months, but contract at 8.