There is no usable lifespan for wire coated lifelines. There are cases of them failing in less than a year from installation. Tightly encasing stainless is litterly the text book example of how to accelerate crevice corrosion, which is why it was banned. Not because people failed to replace it (they tried replacement cycles intervals before the ban).
Sure it works for years on some boats, but I know a lot of people that sail around with all sorts of stupid things installed on their boat, just because they haven't sunk yet doesn't mean it is a good idea.
The sailing authorities that spend huge amounts of money figuring out why sailors die, specifically while underway figured out years ago that coated stainless was dangerous and leads to people being injured. Absent evidence to the contrary, why would you suggest breaking from their recomendations?
No offense intended, but you would have to site a specific example before I can believe that there are cases of vinyl coated lifelines failing in less than a year from corrosion.
I know that there are cases of lifelines and even standing rigging failing in less than a year due to defective parts or incorrect swageing or installation, but in my many years of manufacturing, installing and inspecting rigging and lifelines, I have never once seen what you describe.
If I am wrong, I will be the first to admit it, but you're going to have to do a little better than just stating your opinion.
As far as evidence to the contrary, I can only rely on my nearly two decades of rigging experience in the sub-tropical area where I live and conduct my business. Plus the information and recommendations that I get from the wire manufacturers that I buy my materials from.