the rest of you Fidiots suggesting go until you blow, stitching together with paper clips, replacing with bicycle chains or turn them inside out for extra longevity, can just keep yo moufs shut.
check the belts for cracking across the belt. If you keep an eye on them they will give you plenty of warning before they will just snap. For tension, Deflection between the engine and the pump at the greatest distance should be between 1/2 to 3/4 of inch (Just push on it).