My 7900 isn't used much yet, but after today my experience is similar to these. If I use auto nozzle check, it almost always fails, and requires one or two cleaning cycles. Today it failed even after two cleaning cycles. A manual nozzle pattern appeared perfect.
The past couple of weeks, I have printed a nozzle pattern, and despite appearing perfect even under a loop, if I then enable auto nozzle detection and send the printer a print, it will clean. This has happened on 5 occasions.
At this point I have consumed nearly all of the ink in the starter cartridges (3 have been replaced, the rest are below 5%), and my maintainance tank only has 13% capacity left in it, and only printed a few prints... 1 24x30 and a handful of 17x22.
I called Epson Preferred help today, the tech agreed that this is too much ink consumption and didn't feel it was normal. They had me do one service check which showed the AID (auto ink detection) unit was OK. He said a tech would call tomorrow to schedule a visit on Thursday.
So currently I am not using this feature and am quite happy with the output. I'll report back after they look at the machine.