Canon ipf6400 - extending the maintenance cartridge life

Six months ago we have acquired a second hand canon ipf6400 which we use for banners and signs every month or so. It's working well, but it seems that the maintenance cartridge needs to be replaced very frequently as we have already used two of them. All the cleaning were triggered at power-on by the software and never by operator's choice.

Are there any best practices to extend the life of the maintenance cartridge? The cost of replacing it is adding up fast considering our limited use of the printer. Thanks in advance for any insight!