I was wondering about this question,can only people who have tested it answer please, if you have a possible answer but can't be sure put it as a comment, thanks
Going by this answer to a different question as my source because no other website I've checked seems to have duration, it looks like the duration of each level
- Level 1: 10 second freeze, 60 second cooldown
- Level 2: 20 second freeze, 90 second cooldown
- Level 3: 30 second freeze, 120 second cooldown
Remember the freeze is broken instantly whenever you attack someone, so it's not really a paralyze-type shout, but more of a take-out-of-the-equation-for-a-while-type shout. It's useful, for example, to freeze a higher level opponent solid to deal with his minions first.