How long should a reguler interval ending?

I have pcos my period are always 7-15 days long, I want to know how long a reguler time of year suppose to last Us near PCOS is usually a little longer. Mine sometimes final anywhere from 5-12 days. Usually 5-7 on the good ones. Most run of the mill periods final around 3-7 days.
Anywhere from 3 to 7 days coming every 28 days.