Old climbing ropes still very strong if not damaged in some way.

"These facts also hold for 10- or even 15-year-old ropes. This has been proved by many tests of such old ropes (not even 25-year-old ropes and one 30-year-old rope broke in tests in accor- dance with the standard; they still held at least one drop; this means that they will not break in practice, unless loaded over a sharp edge, in which case they may break)."

http://www.caimateriali.org/fileadmin/us...rnal_3-2000.pdf

1" Tube loses only about 1.5% per year too.

"This is about a ~1.45% decrease in strength relative to the original breaking strength per year."

http://itrsonline.org/wordpress/wp-conte...bbing-paper.pdf