Has anyone ever figured out exactly what a "deep clean" is?

[mikling]

MIS very specifically warns against this operation and they give no reason.
I think the reason is that there is a real risk of ingesting air into the printhead channels. This is not a problem with OEM virgin carts but is distinctly an issue with older or gooped up carts as well as compatibles. ( BTW I have done some testing which distinctly shows that the compatibles don't like to "give" out ink all that readily. They're within tolerance when new but when reused you need to be careful.)
In normal cleaning, the pull is not strong enough to take big bubbles down but when the suction is long and strong air getting in there is a higher risk. We all know the pain of getting air into the printhead and then trying to get it out.
With well maintained carts like experienced users would have no problems, with iffy carts it is another story.

 

[hpnetserver]

If your cartridge has such resistance in giving up its ink to a deep cleaning cycle I will think the cartridge and ink combination is bad quality. You should always do a nozzle check after each cleaning cycle (deep or light) to make sure it is ink not air that reaches the print head. If it is air you should toss the cartridge. You should seriously consider if the ink is problematic as well.

 

[fadeaway]

FYI:
To give you an idea of ink consumption, here are the specifications for my PIXMA IP4000 (from the service manual). The amounts are in grams which should be a close approximation to a ml or cc. This printer has one pigment "Black", and four dye-based "Colors"; Cyan, Magenta, Yellow, Black.

Manual Cleaning
0.14 (Black)
0.50 (Color)

Deep Cleaning
1.58 (Black)
1.00 (Color)

Print Head Replacement
0.45 (Black)
1.50 (Color)

Cartridge Replacement
0.30 (Black)
1.00 (Color)

The one that stands out is the large amount of pigment ink used on the deep cleaning. It only leads me to believe that Canon anticipated that major clogs would typically be the result of the black pigment rather than the dye-based inks.

I don't have any information on how the different cleaning cycles may affect the printhead longevity.

 

[Nifty]

If that info is correct, then there are a lot of black manual cleanings (about 11) to go before adding up to a deap clean.