How long after speaking with references would a job offer go out?

Potential job spoke with my references last week. They have been really fast with the whole process up until now and I was expecting to hear from them on Friday last week. How long does it typically take to get back? And what’s the etiquette for me following up if I don’t hear back?

Once you get to the references level is there much of chance of NOT getting the job? I figured it was more of a formality, unless the references are really bad (which I know mine are really good).