Chris over at RevitDialog had a post on quickly purging unused views. Each of us find ways to speed up what could be a very mundane task. One word of caution with this method:
If you create a schedule or organize the project browser to display your unused views, there is a flaw that comes into play with the parent/child views (duplicate as dependant). Even if the child is on a sheet the parent shows up as an unplaced view but if you purge (delete) the view, then you also delete the child view possibly without even knowing it.
Here are some images on the setup for your project browser:
The most important is to filter by the Sheet Number (Equal to <None>) and Sheet Name (Equal to <None>) Similar setup for doing this with a schedule.
Here is the issue that one will face:
Same issue with the schedule:
Seems like an oversight by Autodesk but something to be very cautious of. Don't know if there is some way for a combined reference to be written to the parent view by the coders.