There must be an EEPROM or counter chip somewhere in the toner module that has an ID and running total of number of pages printed. You can get dongles that reset it for you but unless you're going to be buying a lot of different brand toner it won't be worth while to buy it.

In theory the original toner is designed and tested to work with the printer whilst the compatible toner may just be whatever the refiller people just put in there. You're looking for a new printer anyway so if it does go bad you've not lost anything by using the cheap toner.