The paper utilizes the continuous-time Markov chain for modeling the processes of the gradual aging with maintenance on a finite discrete set of an intermediate failure states. The transitions occur according to the birth-and death process and the unit fails completely after visit the last available state. The unit of a multiple and single use is studied. The switching of the repair facility is performed by a hysteresis control policy. We provide the expressions for the stationary and non-stationary performance characteristics, solution of optimization problems and sensitivity analysis of the reliability measures.