Hello,
do you have to replace fluid in antec khuler 620 at any point in time? I am interested in the all in one option, and have never had a liquid cooler before.
No, the whole cooler is sealed. Basically, if you change anything about the cooler, you are doing something wrong. Haha! You just put it in the case, put on the fans, and you are set.
Though the H60/H20620's may seem like "good" choices, they are outperformed by the cooler master hyper 212+ and many other heatsinks that are much cheaper.
the moto with water cooling is that if you want to water cool, go big as air cooling will do better compared to small liquid coolers. the noctua d14 cooler or the thermalright silver arrow are the best air coolers