Fortunately, the grace period can be removed so that you will have to type your sudo password every time you want to perform a privileged task. This makes for a much more secure system, preventing other applications or widgets from being able to hijack this access. Simply add this line to your /etc/sudoers file:
Defaults:ALL timestamp_timeout=0
[robg adds: To edit the sudoers file, you'll need to use a special program called visudo, which must itself be run as root via sudo (got that?). So just type sudo visudo, and edit away (it's a version of vi).]

