It takes about 125 miles to gain that altitude going W-E. Going E-W, once you get to the continental divide you lose that in 125 miles. In September I saw a guy pulling a large, heavily loaded trailer up to the divide from Cumberland. He was riding with who appeared to be his family, which included two children. Seemed like he was carrying nearly all the gear. Despite the relatvely easy grade, he was laboring because of the heavy load. Felt sorry for the guy.

You can certainly speed down the descent if you want. At one point I was sustaining about 21 mph fully loaded without working hard, but I slowed it down after I almost hit a ballast stone. I had a horrible sleep the last night before and was tired. I didn't want to do something stupid that would put me in the hospital and end my trip as I was riding home to Philly. If you simply pedal easily you won't end up speeding.