Custom Loop
I've been using it for a few years in an EK custom loop in rigid tubes, sometimes also using the EK dye pack (special watercooling dye for custom colours). I have good temperatures and no worries about maintenance. I haven't had any residue or any particular discolouration of the acrylic tubes, tank, etc (apart from yellowing from the sun).
I replace the liquid every year as recommended by EK.
The lifespan of the product sealed and stored in good conditions is now 4 years, which is a very good point.