Really has as much to do with what coolant you are using as to what is the best interval. To the OP, I would agree that changing it is prudent. I am rather extreme on my coolant change intervals in that I will not go beyond 3 years in most instances. I have grown real partial to the Heavy Duty red ELC coolants that are designed for some very long intervals in terms of both miles or time, even if I can't get beyond my comfort level of 3 years. I may over time.
I have grown especially fond of the Peak Global Final Charge product. I have used it for many years in my commercial heavy trucks, and it is the fill on everything else I own from my Cadillac CTS, my Silverado 2500, my JD Gator, and my NH compact. I had a discussion with the tech support guys at Peak regarding this, and they designed the product to be a all fleet solution. One world, one coolant philosophy. It has a 1 million mile / 8 yr / 20,000 hour service life. 250,000 mile service life for smaller personal vehicles, but the 8 yr still applies. Eventually I may grow to embrace the longer coolant intervals. I am an old dog and it is hard to change. Even on my commercial stuff, I will go to 500,000 miles or 4 years, but that is all I my comfort level can endure. No proof that it can't go longer.
The Rotella stuff mentioned by CADplans falls into the same similar category as the Peak Final Charge I am using. Delo also has their version of the similar stuff as well. And all the heavy commercial OEM dealerships have house brand versions that are pretty much the same thing also. All of them, including the major name brands, are very cost effective and do a stellar job.