If an inmate who has had their privileges revoked, no calls or messaging; no contact visits, how long are they revoked for?

There is no set amount of time. It could be a couple of weeks to over a year depending on the severity of the offenses and if the inmate was contrite about what they did. When I got to FCI Miami, they put me in the SHU for a week. I did time with a guy that was caught with a cellphone and was already there nine months when i arrived. He was there a few more months and I heard they shipped him across the country to finish his sentence. It can get ugly if they are pissed at you.