As routine maintenance on the systems I put together for customers, I would as a matter of course give everything a good visual inspection. Every year for systems with a high cycling rate (gaming) I would lift the CPU block, clean off the old TIM and reapply new thermal grease. While the block is out of the system, I usually as a matter of course, disassemble the CPU block and (very carefully) flush out the cooling channels in the block and then reassemble. If the O-ring is not elastic (showing signs of stiffness or brittleness) then it needs to be replaced. Depending on the cooling parameters the owner is experiencing I might also change the jet plate in the block (You should have 3 or 4 alternate jet plates with the EK block, including a blank should you wish to machine you own). The water channels (in the EK), or microfin block (other blocks including my Apogee) can quite easily become clogged over time due to deposits that sediment out from even the purest coolant (worse when some ready-to-use coolants are used). So, your maintenance regime will probably fall into one of three categories: 1. None. Fill and forget. A surprising number of people who build a system never change anything unless a core system component is upgraded. Not necessarily a recipe for disaster, but cooling efficiency will drop away over time. More so if the radiator isn't cleaned regularly. 2. Routine loop flush. Probably the most common form of maintenance. Drain the loop, fill with distilled water and run (system obviously doesn't need to be running), drain and repeat if desired. Refill with new coolant, replace antibacterial/anticorrosive if used, bleed. Good to go. 3. CPU block teardown, check for signs of brittleness/discolouration in tubing (not a problem with Tygon in general unless the system is getting a lot of UV (Sun) exposure), check fittings and drain/flush/replace coolant. How involved you want to get is entirely up to you. When making suggestions on your loop I factored in that not everyone adheres to a fastidious regime of tinkering/tweaking etc., hence pointing you towards a low-maintenance EK block, and virtually no maintenance Tygon tubing and fittings.