Short answer: Yes!

Long answer: In the mid-20th c. a standard hairstyle for women would take a substantial amount of time, and need to be "set." Usually, a perm was applied on a regular basis to those with straight hair, and then the hair was "set" as needed (ranging from only for special events to every evening depending on the person.) The hair itself was washed infrequently, twice a week at most, and then re-set afterwards. Most women did bath more frequently, however.

The process of washing your hair was ultimately a very time consuming process, so it makes sense that this would not be done on a daily basis.

Though I have many anecdotal stories, including ones done as research interviews while researching historical costumes and dressing re-enactors for a large museum with a historical re-enacting side to it, I also have an extensive collection of vintage styling, charm, behavior, and etiquette books that I occasionally reference for technique.

This is my first time posting here, but I hope these will constitute primary sources here on /r/AskHistorians.

Veronica Dengle, who is personally my favorite how-to writer on the topic from the mid-century outlines a process of washing hair that involves making liquid shampoo from a solid bar that has combined with warm water and scrubbing your hair vigorously to get the dirt out, paying attention to the parts where dirt will gather. After washing it, several rinses of clean water are applied, and then the hair should be dried outdoors whenever possible. Then, a woman is to brush out and re-set her hair, dampening it with Toilet Water, which referred to a type of scented water and not...ahem...the water from our toilets.

Her recommendation for timing: "If you shampoo your hair every week, perhaps two soapings will be enough. But if you live in the city, or shampoo your hair every ten days to two weeks a third soaping is advisable." (Personality Unlimited: The Beauty Blue Book, 1943)

Several other books I have of a similar type outline the same process. The last book I have that references this type of extensive hair washing process is a workbook from a curriculum published in 1964 entitled "Charm."

In short, the process of washing your hair was ultimately a very time consuming process, so it makes sense that this would not be done on a daily basis and could take a whole evening if someone wanted an excuse to not go out with someone!