I am currently building a deck and as with most do it yourselfers, its taking me much longer than planned. The stacks of 2x10 PT dougfir have been sitting in the sun a while, shrinking, bending, warping, etc. The piles of 10footers are looking pretty bad. At least 5% might be ok for blocking. The 20 and 24 footers however still look beautiful. On my next load I'm inclined to order 20 footers and just cut them in half. The price per foot is the same. Are these longer boards cut from a better part of the tree?
Longer boards are usually cut from heartwood. You should check the moisture content of the wood before you decide to install it. Usually it is better to let pressure treated wood dry out a bit if you can to avoid shrinkage post installation. I like to use boards with 8% to 12% or less moisture content whenever possible.