Moving Server Database Live!

The company that hosts the web based software my company uses to run its business announced on the Wednesday that on Thursday evening it would be doing routine maintenance to move the software to a new site. This continued, without further notification of outages, until at least noon of Friday morning, impacting users.
As an IT professional, do you do major changes like this during times when users are expecting to have full access to the system they use to run their business?