According to the Passive Enduring Kolto which stats "Increases the duration of Kolto Probe by 3 seconds. Additionaly, Stim Bost grants Enduring Kolto when activated, making your next Kolto Infusion or Kolto Injection activate instantly," Kolto probe should remain on the target for 21 seconds. This duration is stated in the tool tip for the ability Kolto Probe. When speced into a dps discipline, the duration that Kolto Probe remains on the target is 18 seconds. This duration is stated in the tool tip. However when in Medicine, Kolto probe should remain on the target for 21 seconds. When Kolto Probe is placed on the target it only lasts for 18 seconds.