51 ashton makes an interesting point. If the seal ran completely dry it would toast itself. I have personally used both rope and 1 and 2 piece rubber seals and so far none has been 100% drip free after a few years, but no clutch problems have resulted either.
It is not easy to find rope seals any more. In my amateur opinion they are less fragile and if stuffed into their grooves tightly and cut off perfectly flush with the block seem indestructable. Stufffing the upper half of a rope seal really tightly into its groove with the crankshaft in place seems like an impossible assignment. A "slim jim" will pull it into place helped by rotating the crankshaft as you pull but that stretches the rope, the opposite of stuffing it.
The rubber seals have the advantage that you can rotate them slightly in the groove so their ends don't exactly coincide with the parting line between the main cap and block.
