I don't know, but it's funny that you bring it up.. I was changing the oil yesterday in the 2000 Jeep Cherokee we've somehow adopted and figured I might as well do the coolant...
it only has like 50k miles on it but the coolant looked kinda like it could use to be changed just because it was kinda mirky.
I say do it.. why not? it's cheap and relatively easy.
I also threw a new radiator cap on there for good measure. Not like it was overheating or anything, but it was like 4 bucks at NAPA. If it was anything other than the jeep i'da gotten an OEM one, but NAPA's cheap mexican parts are basically OEM for the Jeep anyways.
I don't know... interested to hear what others say.