Yes, it's very common to start climbing around 4AM or 5AM, reach the top around noon, and descend and be down around 3:00-4:00PM. That's what I did a few years ago. I was on a tour and we had to start the descent at the certain time to make the bus departure. I had to turn back two stations from the top. I'm climbing again next weekend since I failed last time. Before my last trip, I'd never done cardio in my life. This time, I've been an avid runner the last two years and am in much better shape.

Anyway, I plan to start climbing around 6AM and do not expect any trouble getting back before sundown. Keep in mind, it will be cold when you get close to the top. Bring a backpack with some type of light, cold weather clothing. There's a good chance it will rain for part of the time too, so be prepared for that.