What are the limits for simultaneous tasks on DS 7.1

Hello! 

I have a doubt about Symantec Deployment Solution.

We can create a job for thousands machines and run as a task, Is that correct?
So, how many such tasks can run simultaneously? 
I heard that only three tasks  are recommended... but I guess that number is too little for such a robust tool such as Symantec Deployment Solution 7.1