When to replace the hoses

[Sysop]

The outer rubber is there to protect the steel wire reinforcement braid...if the wire braid is worn through and you feel raw edges of broken wire then change them right away....if the wire is not chaffed or rusted bad then keep an eye on them, they will eventually fail when you are lifting something really heavy and working it hard when they rust

+1 and spraying the bare steel braid with a bit of rustoleum would likely help them last from rusting a bit longer.