Humans can go a long time if need be between a full-on scrub.
I've read many times that in the Middle Ages Europeans took baths twice a year or so.
Trying to stay reasonably clean has merit in terms of infection control, etc. In hurricane or earthquake aftermath scenarios you're likely to be constantly getting small scratches & such while clearing debris and other recovery efforts. Allocating some resources for sponge-baths is prudent where possible.