Id ask the repairer to prove that your inks resulted in printer failure. You can reference http://www.magnusonproducts.com/magnusonmoss.htm but its wording is more to auto work.
The fact of the matter is they cant void your warranty based just on you not using the over priced parts they demand...
If you can, try to avoid soaking the top of the ink sponge. This cart is somewhat new to me but it seems to react like the HP 23/78 etc. when it comes to overfilling. (aka, short term good, long term backfire)
Hope it continues to work well!!!
Des