There is a difference between "routine maintenance" and "preventative maintenance". Oftentimes people confuse the two.

Fluids, including engine oil and coolant, as well as power steering fluid, differential oil, transmission fluid, etc., are changed on a regular schedule to ensure that they have not "worn out." This is preventative maintenance, and it should *always* be followed. Failure to do so means that the fluid will "wear out" and one or more protective qualities of it will be compromised. This WILL result in premature wear and failure of one or more components. The only questions are "when" and "how much."

So yes, follow the recommended schedule to change your coolant, as well as the rest. And the "expense-wise" you reference is a fool's paradise; it's irrelevant. If it costs you $150 to change the coolant (which is way high, average is around $100), how much does that compare to the cost of premature radiator failure, premature water pump replacement, being stranded and towed or, worst case scenario, serious engine damage?

Good luck.