For what its worth;
My neighbor has run summer fuel in everything for years, with no issue. He WILL NOT buy Coop fuel...
If the winter is particularly cold, he will add some antigel to the tank he is filling. Higher cetene ratings apparently.
I have been running 15 year old diesel in my White for two years now. I ended up with 200+ gallons of the stuff, and I couldnt justify using it to start fires or just in the parts washer. I throw some diesel kleen in each tank, and have had little issue with the exception of cold weather starts being a little tougher. Diesel isnt like gasoline... it wont rot in a month or two. (now it seems a week or two)