Another who is surprised by the yeti comments they were standard issue when I was in mountain rescue and they lasted well enough, as Brewsher says silicon them on,best to have a dedicated pair of boots for them and just leave them on the boots permanent.
This was the same conclusion I came to. Fit them to winter boots and leave them on. Mine lasted several years of fairly hard use.
Now I use Outdoor Research Crocodiles. Very pleased with these, they are very well made from high quality materials, I will buy another pair when I see them and put them in stock. They are only available in black though.