An image forming apparatus includes a replacement time predicting circuit, a variation determining circuit, and a replacement time adjusting circuit. The replacement time predicting circuit periodically predicts, based on a consumption trend, a replacement time of a consumption article starting from a time when a replacement article is ordered, the replacement time being a time when a non-consumption amount of the consumption article is equal to or less than a specific replacement threshold. The variation determining circuit determines a variation of each later-predicted replacement time from a replacement time that is predicted when the replacement article is ordered, each later-predicted replacement time being predicted after the replacement article is ordered. The replacement time adjusting circuit, in response to the variation determined by the variation determining circuit, changes the consumption trend of the consumption article so as to reduce or eliminate the variation.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. An image forming apparatus comprising: a replacement time predicting circuit that periodically predicts, based on a consumption trend, a replacement time of a consumption article starting from a time when a replacement article is ordered, the replacement time being a time when a non-consumption amount of the consumption article is equal to or less than a specific replacement threshold; a variation determining circuit that determines a variation of each later-predicted replacement time from a replacement time that is predicted when the replacement article is ordered, each later-predicted replacement time being predicted after the replacement article is ordered; and a replacement time adjusting circuit that changes, in response to the variation determined by the variation determining circuit, the consumption trend of the consumption article so as to reduce or eliminate the variation. 2. The image forming apparatus according to claim 1, wherein the replacement time adjusting circuit changes the consumption trend so as to reduce or eliminate the variation when at least one of a case where a later-predicted replacement time is detected to become earlier than the replacement time that is predicted when the replacement article is ordered, a case where a later-predicted replacement time is detected to become later than the replacement time that is predicted when the replacement article is ordered, and a case where a later-predicted replacement time is detected to become earlier or detected to become later than the replacement time that is predicted when the replacement article is ordered, is satisfied. 3. The image forming apparatus according to claim 1 further comprising: a replacement article ordering circuit that orders the replacement article automatically or after receiving an ordering request from a user, when a time period to the replacement time that is predicted when the replacement article is ordered is equal to or less than a specific ordering threshold. 4. The image forming apparatus according to claim 1, wherein the consumption article is a cartridge storing a color material, the replacement time predicting circuit predicts a replacement time of the cartridge based on a remaining amount and a consumption trend of the color material, and the replacement time adjusting circuit changes a setting of a consumption amount of the color material so as to reduce or eliminate the variation, the setting of the consumption amount of the color material being able to adjust the consumption trend. 5. A non-transitory computer-readable recording medium storing a replacement time management program which causes a computer to execute: periodically predicting, based on a consumption trend, a replacement time of a consumption article starting from a time when a replacement article is ordered, the replacement time being a time when a non-consumption amount of the consumption article is equal to or less than a specific replacement threshold; determining a variation of each later-predicted replacement time from a replacement time that is predicted when the replacement article is ordered, each later-predicted replacement time being predicted after the replacement article is ordered; and changing, in response to the determined variation, the consumption trend of the consumption article so as to reduce or eliminate the variation.