Some 5 years ago I bought a CISS for my Canon IP4500 from cityinkexpress Ltd.On Last Saturday evening, while printing a photo, the magenta ceased working. The ink was not flowing from the magenta main tank and it was noticed that this was also occurring on the Black inks. This was possibly caused by leaks from the air valve or the silicon seal at the cartridges.
A mail was sent to cityinkexpress Ltd on Sunday asking if any spares were available. A reply was received at 20:10 on Sunday evening (!) asking for my address.
This morning (Tuesday)a package was received containing 5 air valves, 5 tank bungs and 3 silicon inserts - all FOC.
As after sales service for a not really high value sale, made some years ago, I'm really rather impressed.