CLC water-coolers dont require any maintenance other than dusting the rad every now and then. Everything is pre-assembled and already filled, all you have to do is mount it to the CPU and case, then plug into power.
DukeOvilla :
Closed water cooler FTW!
Full water cooled systems are a pain to set up, and maintain.
Agree on the setup, but its a one time thing so its not that big of an issue.
Maintanence, if you do everything properly, you wont have to touch the thing at all except for changing the water every 6 months or so. If you use a dye and get aluminium components, I can guarantee you'l have to pull it apart every two months to clean.
TBH, if your going for a CLC water cooler, get an air cooler like an NH-D14. They perform the same and are cheaper, with less possible points of failure.