Hi,
Today the maintenance period kicked in and a number of my team were generating test cases at the time and hit the Save Changes button. The site returned the maintenance error warning and all of their work was lost.
We try and save as much as we can but I'm just imagining if I was half way through a 50 odd step script and I lost this work I would probably have a partial breakdown. 
A pretty simple enhancement will go some way to mitigate against this happening is the addition of an alerts banner that sits at the top of the page and is only visible when you have notices to your users and then you can warn users of the incoming maintenance update in advance so that gives the user the ability to save their work.