I would not recommend the use of treadmill for gait training following uncemented approach as you know it is non weight bearing for first 6 weeks and partial weight bearing after 12 weeks. Moreover, gait training require a lot of support from walking aids and required level surfaces for gaining good balance and in treadmill due to slopped and sliding nature, it is difficult to achieve that. The use of treadmill for many times a days depend upon the particular regime for what it is being used, like stroke, cardiac rehabiliatation, etc. Adding suspension therapy by suspending an individual from the shoulders by supports by suspension therapy apparatus while using treadmill is a good idea but you have to be sure of the safety of your patient and his weight bearing status and also the capability of the patient to cooperate during the exercise regime. As Suspension therapy along with treadmill is used for gait training following the spinal cord injuries.