Well, my mum went back to college when the three of us were at school, and still held down a job - she went to college nights, and was out to class several nights a week for a number of years while studying for the degree; the opportunity (and encouragement) had been lacking when she left school. Granted this was an undergrad degree, not grad school, but it was at a a time when not all that many people - and very few women - were graduates.
She loved studying, and hugely enjoyed her course; while she never actually worked in the field, she always said that it had given her the confidence to go for promotion a few years alter, after her boss died, when she had been recommended to replace him.