My detach trailers will rot the decks off them at a much faster rate than the tag or deckover trailers where the bed is higher up in the air, allowing air to move under the trailer beck. It also makes a difference where the trailers are parked, on cement, gravel or grass, in a shed or outside, whether they are used in the winter on salted roads, run in the rain or sit all winter in a snow bank. There are so many variables involved its not funny, it hard to compare deck materials. One detach we parked on cement, never ran in the winter and the other we used in the winter and parked it on either grass or gravel, the one used in the winter, we put decks on about ever four years, the other one using the same material would last 10 plus years.
I just pulled the deck off both detach trailers and one trailer had mold growing on the bottom sides of the boards as pulled them off, the boards were rotten and the deck was shot, it was just put on in 2015, oak two inch sawn lumber, the other trailer had oak as well and was over 10 years old and the boards were hard and dry, good solid wood for the most part, with the exception of where we punched holes in the lumber from dropping things on the deck, all similar uses, just different times of year and parked in different area's of the yard.
Just thought I'd toss out some variables that are not mentioned or have been discussed, it all enters into the equation of how long the deck lasts in my opinion or from what I've seen anyhow, thought I'd pass it along and give you guys something else to discuss or ponder over.