I sure love the looks of cedar. But, I've had a lot of difficulty of it splitting when building with it. It seems to require pre-drilling before screwing or nailing.
My choice for decks has been 5/4 pressure treated pine. I build decks with the boards pulled up tightly against one another. It will shrink probably a quarter of an inch when it has dried a few months. That's a good thing - it allows for drainage. At that time I paint it with porch quality paint with some anti-skid powder mixed in with the paint. I think powdered granite holds up better than sand, and it's cheap enough. A little will do-ya.
That will make the surface much safer to walk on when wet. Nothing can be more dangerous than a painted floor when wet. And you can be assured, the deck will be wet every morning from the dew. Let wife bust her azz just once on a wet painted deck on her way out to enjoy a good warm cup of coffee first thing in the morning and you'll understand exactly what I mean ;-)
Like others have said, Thompson's is good for a year. Paint is about the only thing I've found that will hold up for very long on a deck. Of course, you'll loose the beautiful effects of cedar, but that's something you'll have to decide for yourself, i.e. short term beauty, or long term serviceability.
PS For my trailer decks I use a mix of diesel and boiled linseed oil. But that's another subject...
