IT "at risk" dates

We are currently reviewing our process of established IT "at risk" dates during the year which are published well in advance (currently out to January 2014) and which allow fixed dates in the University Calendar for IT related service interruptions.  I believe that we are quite unusual in having this particular luxury embedded in our culture and so far supported (although sometimes a little reluctantly) by the University management.  Some of them would prefer out of hours evening and weekend working usually during holiday periods i.e. holiday for the rest of the University in terms of the academic calendar.  The options we are considering include "Do Nothing" and stay with three periods a year, moving to more frequent calendar but less days "at risk" in each period and less days overall too.  Third option is moving to a more ad hoc arrangement, particularly for high impact services or new projects, perhaps mixed with the second option ie a hybrid approach.  One thing we might need to think about is the label - is "risk" the right word?  perhaps it should be the IT "opportunity" dates or "improving your IT Services" dates because the work is often about addressing a risk through maintenance and housekeeping of systems.  comments welcome.