As long or as short as your like. Time limits are artifacts of physical stages where the venue needs you out so someone else can be on the stage in 30 minutes. The festival is a multiplex with an unlimited number of stages. You’d be limited by the maximum length of your chosen streaming service, but not by us. We also don’t set a minimum length.
Even physical venues are getting flexible. During Auckland Fringe this year one group were running 4 hour shows & either this year or last another performer was running 5 or 10 minute (can’t remember which) one-on-one mini plays to a single audience member.