Depends on the wood, moisture content, how it was cut, where you are keeping them, air flow, etc… Easiest way to be sure is to weight them and write the weight on the blank with a marker. Then weigh them every month or so until you no longer see any weight loss.
Cheers,
Brad
PS: Just noticed you are buying them from a supplier, not making your own… I have no experience buying them like you describe (I have too many sources of free wood around me), and I imagine that they are different from supplier to supplier. Maybe you could ask whoever you buy them from for guidance on their particular blanks.
-- Brad in FL - In Dog I trust... everything else is questionable
