It is managed a life of at least one toner cartridge loaded in an apparatus for forming an image on a recording medium with toner stored in the toner cartridge. A counter counts a remaining amount of each of a plurality of predetermined parameters. A replacement determinant determines that the toner cartridge should be replaced with another one when the remaining amount of any one of the parameters is a predetermined amount or less. A display is operable to display the remaining amount of each of the parameters as a percentage relative to a full remaining amount thereof. A selector selects one of the parameters indicating the lowest remaining amount as the remaining amount displayed on the display.