There is no way to predict life and a behavior-modifying event can occur at any time. One client called me, post training, to inform me his dog had become suddenly aggressive towards the children walking past his home as they journeyed to school. Some investigation led to the discovery that two boys had harassed the dog earlier in the week: screaming, charging and throwing gravel and sand at the dog. This is just one example but the potential for new fears/anxieties/negative behaviors to develop is always possible because dogs are highly reactionary to their environment and lack the level of cognition required to problem solve difficult scenarios. Should a negative behavior manifest after training is completed, I would assess the behavior and develop a treatment plan to rectify the problem. The cost for this service is dependent upon the hours required.