I had the head on my 9900 replaced in September and it's working even better than when I first got it second-hand ten years ago. The last couple of print jobs were a struggle with the printing starting off fine, then banding half-way through a print. I looked on eBay and only one of many sounded half-way decent. But it's the removal and disposal that was too daunting to wish to contemplate.
I gave a call to my expert an hour away and two weeks later with the head replaced, the printer was back to nearly new and working better than ever. He told me that the head was a new design and more reliable, less issues with streaking and less cleaning to do and so far he's right!. The cost was less than finding a working second-hand 9900 on eBay let alone driving for hours to transport one then dealing with finding four friends with strong backs to pull one up the steps and another back down.
With the 9900 being my only color printer the cost and the replacement was worth it.