As WR2 said, you wont have to change the coolant in the Antec cooler. The reason why, as he said again, is because it is a self contained sealed water cooling unit. This means that all parts are in one part and completley sealed off to prevent loss of coolant or leaks. The main problem is that they are not as efficient as true liquid cooling but again they are also more convinient for novices and as well cheaper.
Most true liquid cooling kits, good ones, require about $300 for the parts and a very big case, the best liquid cooling is triple fan radiators.
So the only problem you will run into with the Khuler is either a fan going bad or, many years down the road, the pump going out.