Just because the distance is less than half doesn't mean your time will descending will be less than half.
Pictures and video are one thing the real thing is quite another. Route finding and various small blocks will slow you down, especially since this is the first time to this rodeo.
Recently, I came down a canyon that turned 2 to 2 1/2 hour trail trip into 3 1/2 hour marathon. The trip down the down the canyon was a 1/3 of the trail trip. I had been up this canyon twice in the winter but never down it during the summer.
