Kenda Small Block 8’s have proven themselves to be as good as any, and better than most, for winter commuting (although stud-less). As a bonus, I feel I can cut through parks, go over gravel and even a wee bit off road using them. They are 700×35 and can take some variety of terrain.
I’ve read about other riders who use the Kenda’s so I think I’m in good company. Otherwise, my physical fitness is ok, not great, but ok. I should be able to pull off 70+ miles. The weather once looked a threat but now seems to be clearing nicely. Should be a good day for 8 hours in the saddle!