So far no problem, but it would be an exceptionally cold winter for us to get ice like you describe. We might get 8 inches in an exceptionally cold spell........ but I will not be around to witness it.
I have new ropes and floats in a bag that I meant to get them replaced this summer but never got around to it. Think I will just wait till next summer now.
I think the ropes and floats have been in there for either three or four years now with no problems.
But I can see how more northern climates or larger BOW's it could be an issue. My pond is only 3 acres so ice movement has not been a problem to date.
I just used cheap rope but my replacements are better quality anchor line rope. My boat is also small so it does not take much of a mooring to hold it. If the ropes were torn off with ice it would not be a big issue to replace them. Not a huge cost or effort involved.
With the concrete blocks I just prepared the ropes with a loop on the end. Dove down with mask, fins and snorkel, slipped the looped end around the concrete with the other end through it, and at the surface cut the rope to length and installed the float with a loop at the end so I could use a snap connector on my boat rope to attach it easily and quickly into the rope.
A couple hours in the water and less than a hundred bucks and I could replace all of them. It would not be a huge issue if they did get damaged by ice some year. It could happen.
I have had concerns of ice damaging my floating dock but so far no problem.