I was reading the FAQ section for Engine Ice and one of the questions was "How often do I need to change it and are there any special requirements?"
Their answer is "Most every coolant product will work best when changed somewhat regularly…at minimum, we’d recommend once a year." which I found a bit surprising.
On the motorcycle I typically change the coolant every 3-4 years and now I'm curious how often everyone else does the old dump n' flush.