Xerox Phaser 7500 Drum Life

[cscce]

I have a customer with several Phaser 7500 printers. This morning they complained that the drum life on them is much shorter than expected.
For example one printer just needed a complete set of drums although it has only printed 46K pages total. Life expectancy should be 80K.
Also, waste containers fill up rather quickly.
I was wondering if perhaps this could be a firmware issue. The firmware is the version installed at the factory.
Versions installed are: System 1.3.8.P / OS 8.80 / PS 3.2.0 / ENG 40.12.1.
I wasn't able to find firmware for this machine on the Xerox website. Is there an update available?
The other possibility that comes to mind is 3rd party toner, although it appears that they are using the real thing (packaging has the Xerox hologram), and the customer believes it to be genuine. But could it be counterfeit? I'll be looking into that further.
Any thoughts?

[Lance15]

Could be firmware related. You probably need to be a Xerox certified partner with access to the Xerox Global Service Net to get the firmware. We used to be, but, didn't work on many Xerox printers under warranty, so we opted out. Life expectancy is also calculated on 5% coverage (pretty much standard across the board). If they print a lot of pictures, they are exceeding the coverage calculations.

This website shows a good visual example of what 5% of B&W print looks like.

What 5 Percent Coverage Page Looks Like

[cscce]

I found a firmware update for the Phaser 7500. This one was released in 2013. On my original search the selected OS was Win 10. No firmware. When I searched under Win 7 the firmware update appeared. This update doesn't address drum life issues but maybe an earlier one did. Time will tell.