I work like a dog day in and day out. day-in and day-out? day in, and day out? , day in and day out? Please advise.
According to NOAD you can leave out the and and drop the hyphens:
day in, day out
continuously or repeatedly over a long period of time.
Day in, day out, I work like a dog.
I work like a dog, day-in and day-out.
In standard British English, you just write "day in day out". In standard American English, you write "day in, day out" or "day in and they out". (http://dictionary.cambridge.org/dictionary/english/day-in-day-out)