It might take 50 years to get as much sunshine as Oz but polyprop will be falling apart anyway within the year. It can't take UV at all. It's purpose does not include rigging of any sort. It's a cheap floating line where degradation and performance is not important. I've tried hardy hemp but it will also fall to UV much more quickly than poyester and I've tried 3 strand buff polyester but found it too soft to work all that well with longevity of splices and I'm now using buff coloured braided polyester which looks the part, performs and lasts well but of course is more fiddly to splice than 3 strand.