Water cooling seems neat, but I feel it's probably high maintenance. Eventually, seals go bad, the liquid itself may even go bad etc. I'm more of a set and forget type person. I have systems that have been running 24/7 for a good 10 straight years without much intervention. I think we are reaching a point where water cooling will in fact become the norm in data centres though, especially with GPU based loads.
I'm kinda looking into an upgrade path for my NAS, mostly the OS, but in order to do that gracefully I need to build another. Those 24 bay rackmount cases are insane expensive now days compared to when I built this one though so think I will just keep riding it out on this system for now. It's been flawless ever since I switched to async mode on the NFS shares.