During almost a year of what I'll call "normal" operation, when I power on the P7000 from a powered off state it pressurizes the inks, moves the head around, and does what seem to be nozzle checks (though I can't be sure) even though all of the automated nozzle checking and cleaning are turned off. I print fairly consistently when I'm here but I am away a few times per year for a few weeks at each time. In the past, when I have left the P7000 sit idle for 3-4 weeks, when I first power it on it does a cleaning. I know that because the LCD says it's cleaning and displays a progress bar. This takes a long time. That's how everything worked 100% of the time before my last absence, when the printer sat idle for around 5 weeks. When I first powered it on after that it did the pressurize/depressurize/pressurize behavior I described for the first time since it was delivered almost a year ago. That was late May and it has behaved like that every time I've powered it on since then. Prints have no quality issues. What's of note here is that it did NOT do any cleaning and it did NOT seem to do what I assume is the nozzle checking. I did print a manual nozzle check and it was perfect. I have actually never seen an imperfect nozzle check from this printer, which seems remarkable. Also of note is that I purchased a LLK ink cartridge about a month before my last absence because that ink was very low and I expected to replace it at any moment.
Recalling the behavior of my 7900, it did not clean if the ink was too low and would leave you "stuck" until the low cartridge was replaced. Today I started wondering if the new behavior I'm seeing in the P7000 is just what it does when it wants to clean but can't because there is an ink cartridge that's too low. If so, it's a lot better than forcing you to swap cartridges back and forth when no cleaning is actually needed. So, I powered the printer on and it did the pressurize/depressurize/pressurize behavior. Then I printed a perfect nozzle check. Then I swapped out the nearly empty LLK ink cartridge for the new one. When I closed the ink door it pressurized the ink, leaving things where they were before I swapped cartridges. Then I powered the printer off, waited a couple minutes, and powered it on. It started up, pressurized the inks, depressurized them, started a cleaning ("Cleaning" w/ progress bar on the LCD) with the inks depressurized, pressurized the inks around 20% (not sure exactly) of the way through the cleaning, finished the cleaning, immediately started a second cleaning, and was then ready to load paper. Hmmm. So then I powered the printer off, waited a couple minutes, and powered it on again. It behaved "normally", like it did prior to my last absence, with one ink pressurization, and what appears to be nozzle checking, etc., followed by the load paper prompt. I have cycled power a few times since and it continues to behave "normally".
At this point I think there is nothing wrong with the printer. When the firmware thinks a cleaning should be done (powered off for several weeks) but a cleaning cannot be done (because an ink cartridge is too low) it behaves as I originally described with the pressurize/depressurize/pressurize cycle.
Also of note is the fact that ink use of the P7000 is much more even across the different colors, including O and G. Like the 7900, the P7000 seems to use LK quickly followed by LLK, but unlike the 7900 all of the other inks aren't far behind LLK. I suspect this is because of what I think may be automatic nozzle checks and perhaps abbreviated cleanings that cannot be disabled every time the printer is powered on. I could leave the printer powered on to avoid that by disabling the power off timer (that has a max of 24 hrs). When the printer is left powered on I notice it makes mechanical noises occasionally without waking up or moving the head. I'm not sure what it's doing. Given that the nozzles were 100% clear without a cleaning (the inks were too low) after sitting idle for 5 weeks, and that I have never seen an imperfect nozzle check in almost a year of operation, it doesn't seem the automatic checks and cleanings are necessary. OTOH, I've never seen a clog on the P7000, so why mess with success?
I hope all of this will help someone.