Why even ask, if folks just do whatever thing comes to mind?Wow! Intense discussion! I just did the power washer in the driveway trick. Simple, safe, cheap
Powerwashing safe? That's plain silly. Of course, on a 23-foot boat strength matters little.
Bleach will weaken them ~ 5-10% each time. For what? I don't shine the tires on my car either; I would find too-clean lines embarasing, like shiny tires.
Washing does not extend the life; the washing always does more damage than the dirt would have. This has been confirmed with testing.
Fabric softener? It's designed to wash-out in water so that it doesn't build up, so it will be gone in a few rains and gone from the rode on the first use. Yes, the line is softer, but that is from the washing lossening things up. Want to replace the spinning lubricants to reduce squeaking and actually do some good? Use a wash-in water repellant treatment; PS discussed this and showed that some can last over 1 year.
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PS did a complete review of the topic, actually testing the lines. Tip: extended soaking (no bleach) and wshing in hot water is manufacturer approved and does less damage than more vigous washing in cold or without the soaking. Machine washing (any type machine) is VERY different from use, in that the core is milked back and forth against the sheath. That does much of the damage.