We recommend that new wood should be sealed right away with Seasonite.  Seasonite is a water-based seal that has no UV block.  Seasonite is made especially for new wood.  Seasonite does a good job protecting wood from water damage while keeping it stable in the first year.   Remember sealing new wood with an oil based UV blocking seal too soon can cause flaking and blotchy unevenness problems when you re-clean the deck in the future.