my guess is that overshoes don't last
Correct. I used to go through a pair each winter. I classed them as consumables!
I think the 'how' of keeping your feet warm is a personally variable thing. What works for one person won't work for another. Depends how sweaty your feet are I guess. So, sadly, trial and error.
Re waterproof socks, in total honesty I'm not sure. My hypothesis is that the waterproofing prevents breathability and wicking of sweat. I reckon if you're going to have a waterproof layer then it either needs to be the shoe itself or an overshoe. I just can't see how a waterproof sock can keep feet warm as well, unless by chance. That is, the weather conditions are right for the sweatyness of your feet... or something like that! That might be a big overlap for some people, I don't know, but I know I personally have not gotten on with sealskinz, ever.
I also think the 'less is more' principle might come into play here too. Put too many layers on, or too thick a pair of socks, and your feet will sweat, the sweat will chill and the end result is - somewhat counter intuitively - cold feet.
I opted for winter shoes last winter (Northwave Farenheits btw, £108 from
Chain Reaction) because my feet were still getting cold in my favoured woolie boolies, shoes and overshoes combo. Previously, in the UK and commuting in London, I had never experienced the need for winter shoes. Here in rural France, with more time on my hands, I ride more often for extended periods in minus C temperatures.
