In reply to MC: The point about claims being made about rope longevity being market driven is a valid one. No manufacturer, particularly in the litiginous age we inhabit, is going to encourage people to use ropes for longer than is absolutely safe. Equally, manufacturers are keen to sell as many ropes as they can.
That said, I think you guys are complete nutters! No way would I lead on ropes that old. I change my ropes every year. A couple of hundred quid is a small price to pay for peace of mind, no?
One of the problems with determining the condition of a rope is that so much of it is invisible, and wear can take place inside the sheath with no apparent damage to the sheath itself. Prolonged climbing on gritstone, for example, will ensure the ingress of sharp particles of rock into the rope.
Then there's the unquantifiable effect of UV light on the fibres. And the amount of falls taken on it. Every fall, even a short slump onto gear, constitutes wear and tear.
I don't think, and you can call me paranoid, that it's worth taking that kind of risk with climbing. If I'm thirty feet above my last runner the last thing I want to be worrying about is whether or not my ropes will snap if I fall.
Another consideration: I climb for the pleasure it gives me. Old ropes, that are so worn that they are difficult to handle, only serve to reduce that pleasure.