As per the title really. I've had the XSPC Eco coolant in my system for 3 years now, but I can't see any signs of discoloration, etc (it was clear coolant to start with though). The PVC pipes seem in good condition, perhaps a bit stiffer than they used to be and contracted slightly judging by the fact the water level has increased a little since I filled it up in 2011. When do you recommend changing it? I've ordered another bottle of coolant anyway.