In reply to JendeHoxar:
Just run it through your hands, paying attention for severe sheath damage, irregularities and flat spots, e.g. as you mention, with a v bend instead of a keyhole shape being a warning sign. It is a reliable method. If you find something of concern, cut it out of the rope.
Rather than retire a whole rope, I tend to remove the knackered bits, which leaves me either with a useful short rope or a useful bit of tat. Damage tends to accumulate toward the ends of the rope unless some particularly traumatic snag/fall occurs.