How long does it take herniated discs at c-4, c-5, c-6, c-7 take to heal?

Varies. The majority (close to 97%) of disk herniations (ruptured or slipped disks) will improve with time. The inflammation (irritation) of the nerves subsides, and so do the symptoms. The process usually takes 6 to 12 weeks, sometimes a bit longer. Sometimes it is quicker. The body will sometimes absorb the herniation, but symptoms can get better even when this does not happen.
6-8 weeks. Most probably you have had these herniations for a long time...You just got an MRI and now see a bunch of herniations....Try physical therapy, medications...If pain persists and you have neruological involvement like arm pain weakness...Than surgery may be necessary otherwise live with it.