The p9000 does a nozzle check when you start it up. It does this regardless of the setting in the menus that allows auto nozzle checks to be disabled - meaning you can't disable this nozzle check. The x900 series did this when they were first introduced, and later firmware updated allowed disabling all nozzle checks except when you swapped black inks. (the p9000 will also do a nozzle check when swapping blacks, which cannot be disabled).
However, the nozzle check uses an insignificant amount of ink ... much less ink than printing a nozzle test pattern. If the nozzle check fails, it will do an auto clean, thus needing ink.
There is a tendency for Epson printers with this feature to get a "false positive" when it checks the nozzles, and do what might be an unnecessary cleaning. I haven't determined if the p9000 is better at this than the previous generation 9900.
So if you want to prevent any nozzle checks and thus prevent any automatic cleanings, you can disable the function in the menu and then leave the printer running all of the time. This may be counter productive, because it seems turning off the machine and allowing it to seal the heads is better for it than letting it run. But YMMV, some users report that leaving it running results in less missing nozzles. I myself always power it down. My p9000 has only done an auto cleaning two or maybe three times when when powering it back up, which actually seems pretty good. (only about 6 months old) I think my 9900 required at least a single channel clean a little more often than that.
I do keep the printer in a humidity controlled room at 40% humidity, something which has helped quite a bit. My 9900 was several years old, and I only replaced one maintenance tank during the time that I owned it, so it didn't really use that much ink in keeping nozzles clean.
