I just built a large, double-deck deck at my son's house in New Orleans. We used grade 1, kiln-dried pressure treated pine for the whole thing. We plan to let it age to a nice grey; no stain, no preservative. Saw a deck built out of the same material that was quite old, no signs of deterioration. The secret is the quality of wood. Not one of our pieces of lumber had a knot anywhere, very true, very staight. All hot-dipped galvanized or stainless screws. 2500lb joist hangers, etc. On the other hand, my brother-in-law in Northern Cal just finished a fancy-schmancy all-redwood deck, far less structural integrity. His stain is already coming off after 1 year. And the whole thing creaks when you walk on it. You can park a truck on mine and it won't bounce. Also, beware of products like Thompson's. There are far superior products out there.