Some programs prefer time limits, others go with a free for all and sometimes they just go by feel. I like to go by feel because even though a structured system is doable, it can also restrict how you feel in a workout. When you're short on time, you want to get in and get out. You make progress or just have fun and goof off; I'm somewhere in the middle.
For the most part it depends on an individuals schedule, they're timing whether its in the morning, afternoon or night and it really depends on their preference and mood. I do believe in making the most out of the time you have but if you want to just have fun and run wild and free than that's your choice. Some of the workouts I've done last no more than 20 minutes. Depending on the physical aspects and my energy levels I keep it at a minimum of 5-10 min.
Animal Workouts can vary depending on the tempo, the amount of exercise, the timing for each exercise and how to incorporate it in a solid amount of work put into it. You don't really need to go very long because many animal movements have you using multiple muscle groups in one solid movement and because of the intensity a lot of them feel, it doesn't take long to get huffing and puffing. Now if you're a wacky speed demon, they'll last even less because you're generating a lot of strength and excess power into the movements as quite a few are very explosive and if you have to move really fast to get to a certain amount of yards, that can wear you out.
I really don't go for speed because just the movements alone and the randomness of a game I play, I challenge my body every time I roll for an animal and move in specific amount of steps. For 20 minutes, I go back and forth playing this game and focusing on the movements and seeing myself as that animal and putting as much effort as possible while maintaining energy levels. I want to be as energized or enough towards the end than what I started with. Going to failure in animal movements is never an issue because it doesn't take long for a movement to bring you down so I do enough to where I still feel it but can keep going without giving out.
Experiment your timed workouts with animal movements and see where you are fitness wise. In reality because these exercises are so much fun, you can do them as long or as little as you want, either way you're benefiting a great deal of building great strength, endurance and agility. Some workouts can wear you out in under 5 minutes if you do it right, others can have you on the ground in 20 so its a matter of finding your right niche. Have fun, be careful and have a blast.
Find out more about Animal Exercise by going to the Wild Animal Section @ ben-bergman.branded.me