From the review at http://luminous-landscape.com/reviews/prin...n-ipf5000.shtml
The heads (two of them) on the iPF 5000 are user interchangeable. The ones on the Epson 4800 aren't. This is a good news / bad news situation. Whereas the heads on the Epson are designed to last effectively for the life of the printer (however long that may be), the Canon heads are intended to eventually require replacement, at a cost of approximately $600 per head (there are two).
This is not as serious an issue as would first appear. According to available information, results from their W series printers, which were released last year, and which use the same head technology as the iPF 5000, show that average head life works out to be approximately 11,500 A3 sized prints (11X17"), with 20% ink coverage per color. How long it will take to make some 11,000 prints will obviously vary by individual. I make an average of 50 – 75 11X17" and 13X19" prints monthly. Assuming worst case, say 100 prints / month, that works out to 110 months – some 9 years. Since I expect the printer to essentially be obsolete in three years at most, and even assuming that the 11,000 odd print number is optimistic, it still means that for all but the heaviest commercial users head replacement cost will simply be a non-issue.
I was curious about whether or not Canon's printer heads changed characteristics as they aged. I have been assured that this was not the case. Apparently the only part that is subject to wearing out is the heater associated with each nozzle. These eventually cease to function, but when they do it is a binary situation. They either work, or they don't. Since the printer automatically bypasses problematic nozzles, it's only when enough of them have failed that the head reports that it needs to be replaced, which, as we've seen, will likely not be for a long time.
No idea what firmware issue she was talking about.