Terminal commands are great for managing a remote computer, writing scripts, or Automating your computer. Here's a handy terminal command that lets you set a delay for sleep and overrides system preferences.
It's not hard to change your system preferences for sleep if you're in front of a computer. But if, for example, you are giving a presentation, you can put this command in the workflow. To set the timer to 60 minutes, the command is:
sudo systemsetup -setcomputersleep 60
If you want the computer to not go to sleep, put NEVER at the end of the command:
sudo systemsetup -setcomputersleep Never
Set or Disable Sleep Due to Mac System Inactivity from the Command Line in OS X | OS X Daily