The headline in this article: Unplanned Work Is Silently Killing IT Departments will not be news to anybody running an IT department.

Despite our best intentions to be proactive, rather than reactive, in IT departments, the problem is that by the nature of technology you cannot help but have to react to issues as they arise. Some of these can be expected, if not entirely planned for.

In my experience, the best way to handle the issue of unexpected work and events was to put aside time in the weekly/daily schedule (a 'reserve') that would be used to catch those elements that didn't fit into the planned schedule. It wasn't perfect, for the simple reason that unplanned work could take up none or all of that time (and more) in a given period, but you could usually even it out over time to a reasonable level.