An in-situ lifespan is predicted for a hydraulic or pneumatic hose assembly for a particular installation, so that the hose assembly may be replaced before failure. A user of the apparatus, e.g. whilst on-site, is prompted to enter basic hose data together with a rating for a number of lifespan factors. The apparatus then determines a basic hose assembly lifespan based on the input hose data, and modifies the basic lifespan based on the ratings for the various lifespan factors. A hose assembly grading system is also described.