Don't know about the 7900, but when I print an Auto Nozzle Check with my 9880 I also get a report on total paper and ink usage, sort of like the odometer on a car. Two years down the road I'm up to 17,500 ml of ink and 136,000 cm of paper on my current printer, and it's still going strong.
However, there is also a deeply buried menu item that tells me how soon I have to replace the docking station, which is the assembly that contains the head wipers etc and I believe I'm pretty close to having to change that thing, ugh! Hope it doesn't require a visit from Epson Boy. That's sort of like the condition of the tires on a used car. So be sure to kick the tires.
There are also some menu items to print head alignment checks. Might be a good idea to run some of those. A printer with bad carriage bearings or such might not be able to print a successfully compensated alignment check. And of course, listen carefully to the sound of the printer when it's printing.