The default timeout of sudo is 15 minutes; that is, sudo will remember your password for 15 minutes by default.

You can modify this default timeout by adding a string in the file /etc/sudoers. However, you don't modify the file directly, but instead you use the command sudo visudo.

So, type sudo visudo in a terminal. This will open up the (actually, a temporary) file for us to edit, using your preferred editor.

Note: if you are using visudo for the first time, you should be asked which editor you would like to use, so choose your editor. There's no "better" editor, but I prefer nano. If you've already used visudo and chose an editor before, but you want to use another editor for the time being, you can do sudo EDITOR=vi visudo to use vi, or change it to nano to use nano. If you want to permanently change your preferred editor, do sudo update-alternatives --config editor.

Look for this line:

Defaults    env_reset

And add timestamp_timeout=X (with a comma) at the end of it, where X is the time you want to set in minutes.

So your line should look like this, as an example:

Defaults    env_reset,timestamp_timeout=5

If you specify 0, you will always be asked the password. If you specify a negative value, the timeout will never expire.

Once done, save and exit.

Source: RootSudoTimeout