Seasonal energy storage plays a key role in low-carbon multi-energy systems (MES) by storing renewable generation in times of excess supply in order to meet energy demands months in the future. Power-to-Hydrogen (PtH2) is being investigated as a promising long-term storage solution for integrated MES. In this preliminary work we investigate under which conditions does PtH2 become a seasonal storage option in district MES through an optimization framework including an uncertainty and sensitivity analysis to evaluate the effect of technological and contextual uncertainty on PtH2 execution. PtH2 becomes vital in low-carbon, renewable-heavy, MES for meeting high thermal demands in winter.