Three factors set video length: platform, objective, viewer
There is no right length. There is a right length for this placement, this ask, and this viewer.
'The three key factors which we consider before selecting the ideal length': the platform ('where are you going to distribute it?'), the objective ('how do you know when your video is successful?'), and the viewer ('who is the ideal video viewer that you are communicating to'). 'Value video' covers 'a commercial, a edutainment video, a video sales letter, a promo video, a corporate video, a video advertisement, a webinar', and a campaign 'can consist of an infinite number of value videos.' Platform numbers as of recording: 'a Facebook video ad placed in the newsfeed can be up to 240 minutes long maximum, while a Facebook story ad can only be 120 seconds'; YouTube in-stream skippable ads 'have to be a minimum of 12 seconds' and are skippable 'after about five seconds'; on your own site with driven traffic 'there are no restrictions.' A kept-up-to-date requirements list sits below the module.
The first question to ask a client who says 'make it 60 seconds': for which placement, and asking for what?