Given an inhouse server running in production mode I would like to keep the impact on the users as low as possible when deploying regular updates (to the server itself, not the user machines .. but that would be a pretty similar problem).

The obvious answer to my question is "at night, when the users are at home". But "night" is a long period of time. Should one start early in the evening to perhaps catch problems with the update early on and be ready to rollback? Or is it better to start early in the morning and use the first users as "guinea pigs" to faster trigger the problems? Or in the middle of the night when the concentration of the one overseeing the update is pretty low but it is guaranteed to have no open file handles of some late working users?

Are there any research papers on the topic?