Replacement Running Backstays

[Oceanroaming]

Ok, A question to all you Rigging Gurus

Statement of my self-made problem - I want to replace my 4 ss-cable running back stays, (Ketch rig) with non-wire rope but don't want to replace it every two years such as all the sales people tell me that I'll have to do with Dyneema or Spectra. Now I know that this problem completely goes away if I just get myself satisfied with the big old heavy 302 SS wires and blocks currently swinging angrily at all of our heads.

Here's the rub. I just came back from a brief sail aboard a custom Abel out of Seattle. We joyfully sailed...(OK, mostly motored) around the San Juans but while aboard, I found this boats running back stays sheathed in a rubber from top to bottom and over the terminus of the block. It was definitely not wire and according to the owner, the rigger said that it's good for 10 years... Now he doesn't remember who the rigger was in Seattle that provided this rig but here's one that uses non-steel, wrapped in a black rubber or (???) to presumably prevent UV damage down to the terminus and is good for 10 years...

Is my info wrong about Dyneema or Spectra? Should I expect these products to last longer than just a short two years? Is there a solution out there, such as the one that I found that works fine for a world cruising boat? I've checked East Coast, West Coast, Europe, Dow-Unda in New Zealand and Australia... the rigger's words are always the same... you gotta replace it every two years.