It can be done in one day but it’s more comfortable to do it in two. But if you plan on two days then you end up carrying more weight which slows you down and justifies doing it in two days. So it’s a cyclical argument.
We decided to summit Mt Adams in one day. Conservative estimate was 14hrs round trip to do the 6,800 ft up and down but we ended up taking 17hrs to get back to the trailhead. Really started to drag above 10,000 ft but I successfully managed to keep my Acute Mountain Sickness at bay with the right breathing techniques and rest. Good thing we had excellent weather on our side so we renegotiated our turn around time and pushed through to the summit. However, due to the delay the glissade chutes had re-frozen with hard rough ice. While sliding down the 30° slopes at 9 mph the skin on my lower back got exposed to all the friction and I got some minor burns. But descending 3000 ft in 60 mins by sliding down a mountain is a fun experience and was the delayed gratification that kept us going up in the first place! The only thing we could’ve done better is plan for more sleep before getting started 🙂
By planning on doing it in one day, we carried less stuff than we usually would for an overnight climb. Which helps us move fast, which in effect also makes you safer and you need less mitigation. Look at what speed can mean: