As long as you watch the lines for chafe wear, they should last quite a long time. I've used similar line for my spin pole bridles for over 2 years now without any trouble. If you do notice a little chafage (stop sitting in the sand with a bathing suit on...!), a few wraps of electrical or sail tape will protect them. Heat shrink tubing should also help as well.
I built those trap lines for Robi, and if they were class legal on the Nacra 20, I'd be using them too. I'll trust 12 strand dyneema or spectra over wire for most any application, with the exeption of standing rigging.