Summary: I was able to extend the life of the original toner cartridges in a Brother HL-4040CN without adding any toner - just by resetting the flag gear in the carts. The description below is what I did for the three colour carts. Presumably the same procedure would work for the black cart...
Further to my previous message on the general success I have had with the HL-5250DN, and with refilling the carts with bulk toner, here are my recent discoveries regarding the drum.
This may apply to many other Brother laser printers, and printers made by Brother. Maybe it applies to other...
I have had good experiences with the toner from the Printer Ink Warehouse:
http://www.ink-refills-ink.com/printer/Brother+HL-5250DN+Toner/5748/
As per their instructions, I found it is necessary to remove the original toner as much as possible before inserting the new toner. I did this by...