Especially with shifters that latch into position instead of simply having an index detent (such as earlier Ergolevers), if the Lo-limit screw is set on the tight side, then each time that the largest rear cog is engaged, the cable gets over-tensioned which accelerates the fatigue cycle to failure of the cable. This gets worse on frames having exposed cable routing (where cyclic frame flexing translated into cyclic cable over-tension, leading to strand failure).