I just created an assessment in Captivate but for some reason I can't find the timing alternative for success/failure captions. For now they are about 3 seconds but I would like to decide the timing of it myself.
Is this not possible in 2019 or in an assessment?
Select the message on stage. Open Timing Properties panel, and you can edit the timing:
If you want to have the same timing for all the Failure (or the Success) messages use the hamburger menu (4 lines top right in the screenshot) and you find the option 'Apply to....'.
Oh of course!
Are you talking about quiz question success / failure captions or for interactive objects set to report to the quiz?