If you are treating patients and don't have access to a second hand in those times where you really do a complete 60 seconds.... (never by the way let's be honest) then maybe move to another hospital/facility.This statement is incorrect. According to the provided link, "Once the battery gets too low on the smartwatch, the gadget goes into a Power Reserve mode that lets you see the time for up to 72 hours from the moment it’s activated — that’s good for checking the time each hour for four times, with each check lasting 4 seconds."
So if I wish to do simple things such as time a patient's pulse, respiratory rate, and other similar timing functions (which take approximately 15-60 seconds per patient) that my dumbwatch would allow me to do, I would not be able to do this with the Apple Watch even in Power Reserve mode. Even using it as a stopwatch or countdown would likely be out of the question based on the short intervals the Power Reserve Mode would allow.
Link: http://bgr.com/2015/03/10/apple-watch-battery-power-reserve/
Again, this is not a complaint. I am still very excited to purchase one for social usage, but simply responding to a poster's original question on what situations would require more than 18 hours. I definitely look forward to greater battery life in the future, but will happy to try one out for what it is as a first generation product.
I don't wear a watch typically (and have never had an issue with a patient's exam) and am getting the apple watch mostly for the notifications on my wrist so I'm not whipping out my phone every 10 seconds. I suspect we won't have issues with battery and work.... Guess time will tell though.