Using a molecular dynamics accelerated relaxation technique introduced previously, the effect of long-term ageing of the amorphous phase change material GeTe is directly considered from a combination of density functional theory and classical molecular dynamics simulations on two different structural models. Results reveal that, with relaxation/ageing, the system evolves following a nearly single Kohlrausch exponential decay for energy, volume and stress, and is mainly driven by the energy relaxation of Te atoms. These features are somewhat unique when compared to other amorphous benchmark systems and highlight the special role of this particular telluride characterized by a stretched exponential parameter $\beta$. The comparison between the virgin melt-quenched and the relaxed state indicates moderate changes in the overall structure, albeit an obvious conversion from octahedral to tetrahedral Ge together with an increase of Ge-Ge homopolar bonds is obtained, which is driven by a modification of the electronic structure, and chemical bonding. Electronic properties with ageing suggest, indeed, that this conversion induces an increased Ge-related population of the conduction band and particularly of the tail close to the Fermi gap, together with a decrease in occupancy of Te(p) valence bands, and an increased electronic localization for tetrahedral Ge motifs. Optical properties under ageing are also considered, and these reveal that while relaxation does not impact the absorbance at higher energy ($$3.5eV),asubstantialreductionisobtainedforenergiescoveringthevisiblespectrum,togetherwithalargeincreaseintheimaginarypartofthepermittivity($_2$)atlowerenergy($$1.0~eV), and subtle changes in bond polarizabilities.