We (meaning -guys with old tractors)often have old antifreeze solutions that have sat in our tractors for long periods of time,also older radiators that are getting fragile.
There is a coolant called Evans c ooolant, very pricy , but I think worth it. Why? because it doesn't need to be changed - and its boiling point is around 350 degrees F. Which to us means no pressure build up. You make the cao so it can't hold any pressure - this helps seals and makes leaks easier to avoid, along with the fact you never add water and never use additives. I know of a few friends that run this (have for years) and swear by it. Because it never boiled nor makes gasses ,there are no steam pockets in the block and head -resulting in even cooling - this helps in head gasket wear and overall engine longevity. Look up evans coolant-you guys may find it interesting , its going in my Kubota - Ferguson soon and in my case this winter after its overhaul.