My harnesses at work are 5 years of properly inspected, and maintained unless any single stress thread is damaged then it's trash
Rope....yes. Depends on how it was used and maintained. Ropes that see a lot of heat from rapple racks and abrasion and dirt will need to be retired sooner than a rope that sees a couple weekends a year.
They say 5 years but that's mainly for liability purposes. There have been tests performed on properly stored ropes a lot older than 5 years and MBS is still about the same as new rope. Use your common sense and proper inspection techniques and you will know when it's time to retire. With that said, I've retired gear after a year (or even less time) when it didn't look right - and this was not some rope that took a core shot. It depends on the sheath and other construction materials as to what works best for the environment you're using it in. Our practice is to always inspect before and after use. On ropes I lay them out and visually inspect the entire length. Any suspect area I pinch to make sure the core is still good since sheath abrasions don't mean the rope is bad.
Not necessarily. Lots of myths in the rope rescue community. For example dropping an aluminum carabiner may cause stress cracks across the axis. Possible? Sure, anything is but probable, no.