When I worked on a floor with mostly PVS patients, we split the showers evenly between all 3 shifts.
Years ago, my Mom (also an RN) worked on an Alzheimer's floor, and one man could not settle down for the night. Turns out he worked odd shifts in the Navy and 3am was the best time to get him into the shower and settle him for the "night" (he slept like a log until 11am-noon.) His family was grateful that they rescheduled the day to fit "his schedule." He was on the specialized unit because of aggression when they tried to get him up for breakfast at 7:30am on the unlocked unit, so this was a case of going with the flow that ended up benefiting everyone, especially the patient.
Also, when Mom was in a SNF before she passed away, she always showered in the middle of the night since she was awake anyway. (30-something years working 3rd shift as an RN will do that to a person!