A sense of humour, Joke, not a serious suggestion, an unrealistic time frame to delay the reboot after a program update.
The other suggestions are more realistic, 10 minutes, 1 hour, etc. these are to allow you to finish off what you might be doing when you did the program update before rebooting.
Ideally it should be as soon as possible so that the update can be finalised, replacing files that would be in use, etc.
