Generally, an elastic optical network (EON) under a dynamic connection (non-uniform bandwidth) set up and termination scenario leads to spectrum fragmentation, and results in higher blocking probability. To overcome this problem, a defragmentation of the spectrum can be applied by reconfiguring some or all connections in the network. However, reconfiguration can interrupt the services of the existing connections if it is not performed in a non-disruptive manner, meaning that no data is lost or interrupted during reconfigurations. In this paper, we propose a different non-disruptive proactive reconfiguration scheme that utilizes the information of holding times (HT) of the connections in order to reduce fragmentation and thus improve resource utilization and minimize the connection blocking. Our reconfiguration method utilizes the HT information, and we allow to reconfigure only such connections, which can be shifted in parallel and without crossing-over the spectrum of other connections. This paves the way for a non-disruptive defragmentation when setting up a new connection. Simulation results show that the reconfiguration with holding time awareness can be effectively utilized to reduce the spectrum fragmentation, and hence results in lower connection blocking probability.