Taking into account quality of transmission (QoT) constraints, wavelength continuity constraint and wavelength integrity constraint when solving the Routing and Wavelength Assignment (RWA) problem in Wavelength-Division Multiplexing (WDM) transparent networks leads to inefficient utilization of network resources and results in higher rejection ratio. This is especially severe when dynamic traffic is considered. In this paper, we investigate the problem of improving network resources utilization efficiency by applying rerouting and set-up delay tolerance, a metric of Service Level Agreement (SLA) that has been exploited in literature for improvement in network performances, taking into account the aforementioned constraints. Moreover, we investigate further improvement in the duration of the service disruption period due to rerouting. As far as we know, this is the first study that exploits traffic rerouting for network with QoT constraints provisioned with set-up delay tolerance to get further improvement in network performances. The performances of the proposed algorithms are evaluated and discussed through extensive numerical experiments. Significant improvements are demonstrated, either in terms of rejection ratio or in terms of service disruption period, in comparison with previously proposed algorithms.