Michael,
In regards to the AIS issues I suspect that they may be largely related to the firmware of the device as a lot of people are having issues with the device being overly sensitive. Epson has said that they are working to address this. But if you've had a number of site visits then there may be something else going on too? Also there used to be an option to buy an extended warranty after the 1 year had expired at a slightly higher rate and assuming that the printer was working correctly, I believe this is still the case.
Regarding warranties in general they are wonderful high margin items that dealers, like ourselves, love to sell. That said, unlike the warranty they tried to sell me when I bought my 4 yo a bike, they can be worth the cost. In production environments many companies require that warranties accompany the purchase of a new printer because they don't want to allocate additional funds for repairs if and when they come up. Since it sounds like you're not in the position where having an out of commission printer is going to cause you to loose money.
Repairs handled under warranty are billed to epson and they contract out repair centers to do the work. You don't have to worry about the cost of parts, time or travel expenses and there is also an expectation of a hasty repair. Out of warranty work is like going to the mechanic, the parts are only part of the bill, what really starts to add up is the cost of labour, and if they replace one part and that doesn't do the trick then you may have to pay for additional visits, which can get pricy. It also will vary depending on the experience of the tech and the ethics of the repair center.
In my experiences high volume printers will generally see issues with paper feed mechanics and pump and cap assembly in the 2-3 year range. These are fixes in the range of a couple hundred bucks usually. If the print head has a problem that an automatic 1K plus fix, although I haven't seen many instances of that aside, from out of the box lemons or in the cases where a head strike causes damage to the head. But it can happen. All in all the 7900 is built for production work, although it arguably is a bit more of a complex machine than the 7880 was. The previous generation epson's were generally very well built, probably the most common repair i've seen in the paper release handle coming loose or breaking on the 24" and 44" printers and the paper feed rollers getting gummed with paper dust on the 17" printers.
I'd say that the odds of a large problem in the second year with light use is pretty slim, a bit more in the third and then getting more and more likely after that, which is why you don't see five year warranties for the printers. Just like the 40K warranty on a car, the problems are likely to start around 50K miles. That's my honest feeling. If you want to do your homework get the name of the closest authorized service center and get a quote for a pump and cap assembly for the printer assuming it's out of warranty and ask what they charge for labour, use that to calculate your risk. Also keep in mind that this is technology, and while the print technology seems like it may have started to plateau a bit, maybe we'll see a full width print head or some great new advancement in ink formulation in a few years and repairing a three year old printer may not be worth it?
In summary i think that the main value of the warranty is to know at the time of purchase that the cost of ownership is fixed for a period of two or three years, and that you can expect a quick fix to any issues. When you're making money from the printer this makes pretty clear sense, when it's lightly used it's less clear.
