As with all auto services, let your car’s owner’s manual dictate how often you need a flush. But as a general rule, Kauffeld recommends a coolant service about every 30,000 miles or five years, whichever comes first. Brad Updegraff, owner of Auto One Complete Car Care in Round Rock, Texas, recommends a coolant flush every 30,000 miles or three years.
https://www.angieslist.com/articles/how-often-should-i-flush-my-radiator.htm
The old green stuff should be changed every 3 years for most engines, 4 years for all cast iron engines. The new antifreezes are good for 5 years or more. This is based on a complete drain, including the block. If you don't drain the block, then you should drain and refill about twice as often. You should change all the hoses every 8-10 years or every other coolant change. A new thermostat with the hoses and a new radiator cap with the hose change is also a good idea.
https://community.cartalk.com/t/flush-vs-drain-and-refill/5183
CARS.COM — For some vehicles, you're advised to change the coolant every 30,000 miles. For others, changing the coolant isn't even on the maintenance schedule. For example, Hyundai says the coolant (what many refer to as antifreeze) in most of its models should be replaced after the first 60,000 miles, then every 30,000 miles after that.
https://www.cars.com/articles/how-often-should-i-change-engine-coolant-1420680853669/
Draining the radiator alone normally should remove 40 to 45% of the coolant. After the first drain, fill the system as well as you can with water, then warm up the engine and let it cool. Drain the radiator again and fill it once more with water. Repeat.
http://www.popularmechanics.com/cars/how-to/a78/1272246/
For most people a drain and refill periodically is all you will ever need. The only time I really recommend an actual coolant flush is if your radiator and cooling system has been contaminated by something (transmission fluid is a common fluid that leaks into the radiator).
http://www.myautorepairadvice.com/coolant_flush.html
Bleed the System. Now comes the hard part–filling the system. If the system holds 12 quarts, you want to install 6 quarts of undiluted antifreeze, or exactly half of the cooling system's capacity. The cooling system has lots of nooks and crannies that trap air, making it difficult to fill the system with coolant.
http://www.popularmechanics.com/cars/how-to/a78/1272246/
The Truth Behind Coolant Flushing. What you may have heard: This is a simple job... You need to use chemicals to get debris out of the radiator or It can only be done at an auto repair shop. The truth: You don't really need anything special to replace the antifreeze in your radiator. You need to be sure and get the right type of coolant and you need to be sure and use an auto repair manual so you know how to drain the radiator, how much fluid to put back in, how to bleed the system, etc.
http://www.myautorepairadvice.com/coolant_flush.html
On still other Mercedes, it's 150,000 miles or 15 years. Some manufacturers recommend changing the coolant more often on vehicles subjected to severe service, such as frequent towing. The schedule for many Chevrolets, though, is to change it at 150,000 miles regardless of how the vehicle is driven. Many service shops, though — including some at dealerships that sell cars with lifetime coolant — say you should do it more often than the maintenance schedule recommends, such as every 30,000 or 50,000 miles.
https://www.cars.com/articles/how-often-should-i-change-engine-coolant-1420680853669/
The cost of a coolant flush typically runs between $100 and $150, according to highly rated mechanics. Kauffeld says this can include four gallons of coolant, a conditioner and a cleaner. CostHelper.com estimates the cost between $54 and $144 for a radiator flush at a standard shop, with an average price of $99.
https://www.angieslist.com/articles/how-often-should-i-flush-my-radiator.htm
Anyway, yes coolant does wear out and needs to be changed. How often is a function of what type of coolant is in the system. I think that a '98 Chevy will have Dex-cool in it (Orange in color) Dex-Cool is supposed to be a 5 year 100,000 mile life, but there are some people that don't believe it.
http://boards.straightdope.com/sdmb/showthread.php?t=480764
how often should you flush your coolant
One should flush their coolant on every 30,000 miles or five years, whichever comes first.