Modern cars carry kilometres of cables. Many of them are exposed to cyclic mechanical loads which might lead to failure of the cable. Often, suitable routings are known, e.g. from previous vehicle series. However, especially for rather new cable types (like high-voltage cables), it is not clear how to assemble the cable to minimize the risk of failure. Thus, wiring harness designers seek for efficient cable lifetime predictions, which help to assess the designed routing (besides other aspects also with respect to lifetime) already during early, purely virtual development phases. In principle, detailed FEM analysis, combined with material SN curves, would allow for those assessments. However, the effort is unreasonably high and such an approach shows to be simply impractical for industrial use. In contrast, we propose a methodology which (1) efficiently describes the cables by geometrically nonlinear rod models [1], enabling interactive, real-time capable simulations (see e.g. [2]) (2) performs a load data analysis especially tailored for slender structures [3], including a stress recovery, the computation of suitable comparison stresses and the rainflow-counting of the load cycles in the comparison stresses, (3) applies a damage calculation which makes use of so-called cable-SN-curves, an innovative concept which is key for absolute lifetime predictions. In our contribution, we will present the above-mentioned methodology and demonstrate the quality of the absolute lifetime estimations in a validation study.