Darco wear seems inevitable. Where it is makes a big difference in how you try to rectify it. Some use beveled edges at the front of a uhmw strip etc. I won't do that because it puts pressure on that strip as it pushes against the wear bar to get up and over it. IMO a uhmw strip, placed where needed, extended past the wear bar so it never comes off is the optimum way. It doesn't take much to elevate the slide enough to slide the uhmw in.
As far as the darco being worn all the way up to the edge I would use the skis. They cover the worn bottom (unless a wider area) then cover the edges and attach under the transition strip. There is no worry about water intrusion with that install if the strip is sealed. OR
you could have Keystone cover the entire bottoms of your slides under warranty with uhmw as I did....works very well. Darco under a slide is a problematic situation with a material that was never meant to slide over a wear bar for any length of time.