Personally I think those are just a waste. I started snowboarding last year at 29, and I am moderately athletic. Needless to say my ass was fine, and same with my wrists. The warning I always heard was your first few days your going to kill you ass and your wrists, neither were true for me. I saw your other thread and you sound way more naturally athletic than I was and far more in shape. The number one thing I can say is lessons, I took 3 lessons last season. My very first day, my second day, and like my 7th. Maybe it was the lessons that kept me off my ass. Either way, don't think I would worry about too much as your probably only going to wear them for 2 days then say fuck it.
........Then again maybe it was the super deep pow we had last year that saved my ass!