i'm running up to the end of my first rope's lifespan, and after waffling on this question for about two days, i decided that if i had enough doubts that i was thinking about whether or not i had enough doubts, that was enough that i'd rather retire it and get a fresh rope just for the peace of mind. so, for me, if it feels like it might be too old, it's too old. i know that's rather conservative, but i don't ever want to be halfway through pulling a crux and then get that nagging thought of 'but will this rope catch me if i fall here??'