Xerox Drum Date or Expiration Date ? What Is It ? For Docucolor 242.252,260

[PrintingFools]

There is a large date stamped on the box of all Xerox Drums.
Is this an expiration date? What is this date and what does it mean.
As I find many drums for sale on ebay and most of the time the sate is from 2011.

Also, two more questions (1) how long should a drum last just sitting in the box ?
(2) How many clicks are you guys getting out of your color drums , before replacement is needed.

I am wondering if something is wrong...because we seem to be going though drums quickly.
We use about 3-4 sets a year and we print about 55,000 13 X 19 (14 point) Full Color Sheets a year on it. (not a lot )

Thanks in advance for your help!