Many of the "high mileage" coolants on the market will create electrolysis over time. Mainly due to the different types of metals the mix must flow over and around.
I have seen many radiators that have gotten eaten from the inside out due to electrolysis. I have always recommended changing the coolant every 2-3 yrs.
I have been using Evans coolant even before I was working for them. It has no water in it and is a lifetime coolant. I just put it in my 2011 Dakota and will be putting it in my 50 Ply wagon.