Alpine rock slopes evolve over long time in changing morpho-climatic settings. In suitable topographic and geomechanical conditions, weakening and increased hydraulic conductivity associated to rock mass damage under gravitational load can result in slow rock slope deformations possibly evolving into fast-moving or catastrophic rockslides. We simulated the long-term evolution of a high-relief alpine slope using a 2D, time-dependent FE numerical model based on static fatigue laws. This simulates slope creep up to tertiary regime explicitly as a function of damage. Model parameters are upscaled from lab to rock mass conditions through a novel approach based on data derived from rock mass characterization. We present a first model test on the rock slope affected by the Spriana rockslide (Central Alps, Italy). We show the ability of damage-based modelling to track long-term evolution from a poorly disturbed rock mass to a mature rockslide system through diffuse and localized damage.