Due to my experience that carrying the gear for a single overnight stay does not really pay, we decided to do the mountain in a single push, that is, car-to-car without camping. Many others have done this before (see a particularly nice report) although the vast majority of climbers does not. My 30-liter daypack was just big enough to contain everything including a long rope.
We set out at sunset shortly after 8 PM, reached Camp Muir at 1:30 AM and had a break there for about two hours. I only took a short nap there - interestingly, in the mountains I need only very little sleep, maybe because of the excitement, exercise, and/or the fresh air. Continuing on the DC route, my friend got slower and slower, and just before 8 AM, I advised her to return with a two-person group coming across us.
Since I wanted to speed up and the snow was still rather hard, I continued on my own without even attempting to rope up with others. I felt this to be really risky only at elevations of about 4000 - 4200 m where an important snow bridge over a mid-size crevasse had crumbled.
On the way up, I needed to navigate a little to find a way to cross the gap in the vicinity, and on the way down I followed the RMI's detour towards the East. On the other hand, the snow sculptures on the way, formed by the sun and wind, were fantastic - see the photos.
During the last about 400 m of ascent I was getting slow myself and really had to force myself upwards. This was not a problem of exhaustion or lack of sleep or nutrition, but due to the thin air. As I found out two weeks later on Mount Whitney, simply to breathe more strongly would have helped a lot.
Finally, I reached the crater rim shortly after 10 AM. It was of course windy and cold, and unfortunately the views were not really good. So I spent just about one hour on the top, crossed the crater, registered myself (writing with cold fingers was not that easy), passed the actual summit (Columbia Crest), and took photos of the steam vents and volcanic rocks.
Since my descent was rather late, the snow was getting soft, and at the lower end of the Disappointment Cleaver there was hazardous rockfall two times. I passed Muir at 3 PM. On the boring Muir Snowfield, running down as fast as I could, I lost my helmet which I had attached to my backpack negligently. When I noticed this, I did not want to return and search for it. I reached Paradise at 5 PM, slightly tired, but no sore muscles or feet, but was glad for the opportunity to take a shower in visitor center.
Later I learned that someone else had found and delivered the helmet to the NPS office in Paradise, who kindly sent me a parcel :-)
¹ To those folks who still adhere to measuring length in multiples of the boot size of their medieval ancestors, sorry for the inconvenience applying a conversion factor of 10 over 3.