Type sudo visudo
and this screen appears:
#
# This file MUST be edited with the 'visudo' command as root.
#
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
#
# See the man page for details on how to write a sudoers file.
#
Defaults env_reset, timestamp_timeout=120
Defaults mail_badpass
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:$
# Host alias specification
# User alias specification
# Cmnd alias specification
# User privilege specification
The first command Defaults env_reset, timestamp_timeout=120
has been modified with a timeout of 120 minutes between having to enter sudo
password. The normal default is 5 minutes. Although you can change this to a very large number you will still have to enter it once per boot.