My trusty aluminium extending ladder has lasted at least 20 years, and is still in very good order - except that the rubber/plastic 'buffers' at the ladder ends have begun to deteriorate. These help grip the walls at the top, and the ground at the bottom, so they do contribute to safety of the ladder unit in use.
Can replacement buffers be obtained from the ladder manufacturers?
Currently they are riveted in place, but I guess that nuts & bolts would work just as well if I have to drill the rivets out.