how many 16"x20" prints can be expected from a new full set of epson
220 mL UltraChrome Ink Cartridges running on an epson 7600 printer?

Hopefully the following information will guide you to the right answer.

I have spoken directly to the Epson customer services department who
deal with this sort of query and the first response was
"That is impossible to know". This depends on how much page coverage
you have, the amount of colours, the print quality and what printing
format you are running.

The good news was that we went through their system and did our best
to work out what the rough estimate would be.

The epson technical support specialist did not have the exact
measurements so the closest we could find was 17 X 22. The cost of
printing each sheet was roughly 85 cents per sheet.

Working on the cost of the cartridges as 85 dollars each this gives
you an estimate of 100 sheets per cartridge set.
The epson engineer mentioned though that this heavily depends upon the
paper coverage, quality and printing type that you are doing and so
could deviate from this quite substantially.

He mentioned that the best way of finding the answer is to do the following.

Before printing the job run a status print and note the amount of ink
that is in the cartridges and how much has been used.
Print ONE copy of the print you will be doing and perform another status print.

From this you can work out how much ink is used per print and thusly
you can work out

220/ X ink used per page = number of pages per cartridge set.

You can also perform a nozzel check which will tell you the same information.

Alternatively you can order a 7800 Epson printer which has statistics
element built in which tells you the ink usage over the past 12 print
jobs and uses a new cartridge system called UltraChrome 3.

I'm sorry I can't be more specific but I don't think the definitive
answer you are looking for is out there.

--Keystroke-ga

Thank you for your quick response.  The information was very
helpful,is this an area(digital printing)of speciality for you?

I managed to get the information out of the Epson customer services
department directly.
Out of interest, why only 3 out of 5 considering your text review?

--Keystroke-ga