This paper presents a comprehensive network design framework to estimate the impact of adopting a given type of line interfaces to support traffic requests along an extended period of network operation. The framework is utilized to compare the effectiveness of deploying 800G-capable embedded and pluggable coherent line interfaces on a reference optical transport network with growing demand for capacity. The simulation results highlight that, in view of their improved optical performance, higher spectral efficiency and flexibility, state-of-the-art embedded line interfaces can be effectively deployed and exploited over a longer period. Particularly, they allow to support the same or more traffic load at the expense of fewer interfaces than that of the consecutive deployment of current and next-generation pluggable line interfaces.