This paper presents a buffer-enabled allocation strategy for Advance Reservation (AR) in dynamic Multiband-EONs, targeting reduced bandwidth blocking probability (BBP) and improved Quality of Service (QoS). Utilizing a Search Depth method, it dynamically allocates buffer resources to optimize service time and network efficiency. Simulations demonstrate that higher Search Depth improves QoS and BBP, especially in networks with shorter distances and higher connectivity. However, increased Search Depth introduces a trade-off with computational complexity.