Exact protocols for cervical immobilization with collars or braces have not been worked out yet. Some studies published so far have tried eight hours/day for three months. This was followed by another three months of intermittent use. Others tried three months of constant use followed by three months of intermittent use.
It's best to have repeat X-rays and MRIs done to show the results of treatment. If the condition has stabilized, then the collar can start to come off gradually. If you wear it constantly, muscle atrophy and weakness may occur. A gradual weaning process will help restore muscle strength and maintain the stability you've gained by wearing the collar.
Your doctor can best advise you on a wearing schedule to start. Changes in the schedule will come automatically with the changes seen on imaging studies.